Sam and Dean are left to pick up the pieces after the loss of their mother, the demise of Crowley and the heartbreaking death of Castiel. Meanwhile the birth of Jack leaves the Winchester brothers with differing opinions on how to deal with a Nephilim. After being dragged into the breach, Mary must learn to survive Lucifer and an apocalyptic world.
Sam and Dean begin to explore what Jack is capable of doing with his powers. An unexpected visit from Donatello alerts the boys to the fact that Jack will need more protection than the Winchesters can provide. There is a new Prince of Hell in town, Asmodeus, and with Lucifer out of the picture, he sets his sights set on Jack.
When it comes to the Stynes, Dean decides to take matters into his own hands. Sam tries to come to terms with his decision.
Dean makes a shocking decision regarding the Mark of Cain that would change not only his life, but Sam’s too. Meanwhile, Crowley and Rowena face off and Castiel gets caught in the middle.
Dean and Sam investigate a bizarre murder and realize the killer bears the same tattoo as those from the Styne family. Eldon Styne attacks Dean and a brutal fight ensues. Meanwhile, Castiel acts as referee when Charlie and Rowena are forced to work together on the Book of the Damned. Crowley discovers his mother is missing and knows she's up to something so he turns to an old enemy for help.
When Claire Novak gets a lead on her mother, Amelia, who has been missing for years, Castiel asks Sam and Dean to help her. Castiel feels guilty for what he did to the Novak family and wants to make amends by reuniting Claire with her mom. However, when they find out what took Amelia, they realize there is a chance Claire may not get her happy ending.
Dean is a demon and running amuck with Crowley while Sam tries to figure out what happened to his brother. Meanwhile, Castiel is dealing with his diminishing grace.
Crowley notices Dean is becoming more and more aggressive. Dean tells him that’s the side effect of being a demon, but Crowley knows it’s something more - the Mark of Cain needs to be fed. Meanwhile, Sam is captured by Cole, an angry man who blames Dean for his father’s death years ago and wants revenge. Cole tortures Sam, hoping he’ll tell him where Dean is hiding. Hannah sees how weak Castiel is becoming as his grace continues to fade, so she makes a bold choice and asks Metatron for help.
Sam continues his efforts to save Dean from the Mark of Cain. Crowley realizes Dean’s demonic antics are starting to cause problems for him in Hell so he searches out an unlikely ally.
A recent string of werewolf attacks points to a surprising culprit – Kate, the werewolf Sam and Dean let live.
When Sam and Dean investigate the disappearance of a teacher, they are stunned to see the school is putting on a musical based on their lives.
Dean is surprised when he checks Bobby’s cell phone and hears a message that says Bobby or his next of kin have been named as a beneficiary in an heiress’ will. Hoping that means extra money, Dean talks Sam into hitting the road to claim their fortune. However, what they encounter at the house is far from a treasure chest.
Sam and Dean stumble upon a demon who is running from Crowley. Before they have a chance to shut him down, Rowena steps in and takes things into her own hands. Realizing Rowena is trying to recruit and train followers in the art of witchcraft, Sam and Dean come up with a plan to catch her before she can do much damage. Meanwhile, Hannah runs into a blast from her vessel’s past, which complicates things for her and Castiel.
Jody Mills reluctantly attends a mandatory sheriff’s retreat and is partnered with an overeager sheriff named Donna who wants to bond. Just as Jody thinks things can’t get any worse, a body with just strings of meat and skin hanging off the bones is discovered. While the local sheriffs blame an animal attack, Jody knows better and calls Sam and Dean.
Castiel finds Jimmy’s daughter Claire in a group home and she convinces him to break her out. After she runs away from him, Castiel calls Sam and Dean to help find her before she gets in trouble. Meanwhile, Crowley faces his biggest challenge yet.
After the massacre at the ranch, Dean, Sam and Castiel double their efforts to find a cure for the Mark of Cain but there is nothing in the lore that can help them. Desperate, Castiel comes up with an idea that Sam deems the "single worst idea I've ever heard." Meanwhile, Rowena continues to plot against Crowley, and Castiel tries to mend his relationship with Claire who is plotting revenge against Dean for killing her friend.
Sam is scanning the internet for suspicious paranormal activity and comes across a video of Charlie beating up a district attorney. Dean suspects she’s back from Oz and hunting on her own, assuming the district attorney must have been a demon. When they do find Charlie, they are shocked when she tells them why she really came back from Oz.
Looking to get Dean out of the bunker, Sam finds a case for him and Dean to investigate – people are disappearing into thin air with only their clothes left behind. Sam and Dean suspect fairies or angels, but the truth turns out to be much more shocking – Hansel, from Hansel and Gretel lore, is kidnapping people and turning them into their younger selves to placate the evil witch. Unfortunately, Dean finds this information out the hard way after he becomes Hansel’s next victim and reverts to his 14 year old self.
A ghost starts killing people through various electronic devices. Sam and Dean discover who was killed and why this ghost is seeking revenge on a group of college students but what they can’t figure out is how he’s doing it. With three dead, the brothers must stop the ghost before he claims his next victim.
Dean, Sam and Castiel deal with Cain’s return. Crowley and Rowena continue to grow closer but when Crowley bails on plans with his mother to help the Winchesters, Rowena lets him have it.
Despite Dean's directive to forget about looking for a cure for the Mark of Cain, Sam continues to do research. Dean suspects Sam is hiding something but decides to focus on a new murder case where they run into Cole. The three team up and learn a Khan worm is infecting men and turning them into murderers. Unfortunately, the worm makes its way into Cole.
Sam and Dean investigate a string of suicides committed by people with little in common other than the identical, grisly method of death – slow, self-administered disembowlment. All of the victims were members of a Catholic church and had recently given confession, leading the brothers to suspect the priest is somehow involved. Meanwhile, when Crowley captures Olivette, the leader of the Grand Coven, Rowena pleads her case to be allowed to practice magic freely again.
Sam and Castiel follow up on a lead about the Mark of Cain. Dean and Rowena meet.
Charlie calls Sam and Dean to tell them she found the Book of the Dead which could help remove the Mark of Cain. The Winchesters race to her after she tells them she’s been shot by a man named Jacob Styne who says the book belongs to his family and he won’t rest until he gets it back. Castiel and Metatron take a road trip to find Castiel’s grace but they hit a couple road bumps along the way.
Sam learns that former Men of Letters, Magnus, once built a magical box and Sam sets out to find it in the hopes it can cure Dean of the Mark of Cain. However, what he’s not prepared for, is the deadly alarm system Magnus set up on the box. When Sam opens the box, he puts both his and Dean’s life in danger.
Picking up where the finale left off, Sam and Dean must deal with the Darkness that has been unleashed. Castiel deals with the effects of Rowena’s spell and recalls his brutal battle with Crowley.
Dean helps Jenna, the deputy he met after the Darkness fell, get back home safely and then sets off to help Sam deal with a town infected by a mysterious and deadly gas. However, when Jenna falls into dangerous hands, she calls Dean for help and Sam tells him to go back to her. Unfortunately for Sam, he isn't able to handle the townspeople turned monsters as easily as he thought.
While Rowena tries to consolidate her power to protect herself from the Winchesters, Sam and Dean search for a missing baby connected to the Darkness. Meanwhile, Castiel struggles to heal and Crowley tries to find a way to use the Darkness for his own personal gain.
Seen entirely from the point of view of the Impala, Sam and Dean go on a road trip to fight monsters and demons.
Sam and Dean investigate a series of murders at a local B&B that also happens to be Lizzie Borden’s old home. When a local man, Len, tells them he saw a little girl around the B&B around the time of the murders, the brothers realize Amara may be responsible.
Castiel seeks out Metatron’s help to stop the Darkness. However, Metatron is pretty happy with his new life as a freelance videographer for the local news and isn’t inclined to help the Winchesters or Castiel. Meanwhile, Crowley is losing his hold on Amara.
Sheriff Donna calls Sam and Dean for help after a horrific murder with supernatural elements happens in her town. Sam continues to have visions and asks God for help, which frustrates Dean.
Sam is shocked when his childhood imaginary friend Sully makes an unexpected appearance. Sam can’t understand why he’d see Sully now but what’s even more surprising is that Dean can see him, too. Flashbacks reveal young Sam’s friendship with Sully and why he needed him.
Amara unleashes her power on the local townspeople as she issues a shocking challenge. Dean tries to better understand the hold Amara has on him, while Sam and Crowley come up with a plan that could have disastrous consequences.
Now that he has Sam in the cage with him, Lucifer offers Sam a way out but it comes with a steep price. Dean and Castiel look into the angel smiting that could have killed Amara.
Sam and Dean investigate a case where people are suffering violent deaths after hearing a mysterious song.
Sam and Dean drop in on Jody Mills, Claire and Alex after receiving a panicked phone call from Claire. She believes the recent murders in town are supernatural and wants the boys’ help. However, Sheriff Mills tells Sam and Dean that Claire has been getting into trouble lately as she’s been attacking normal people and accusing them of being monsters.
Sam and Dean investigate a set of murders on Valentine’s Day and discover they are dealing with an ancient curse. Once kissed by the curse, the person is marked to die.
Hoping to find a weapon powerful enough to defeat Amara, Dean convinces “Castiel,” who is still Lucifer, to send him back in time to the last reported sighting of the Hand of God. Lucifer sees the potential in getting his hands on this weapon so goes along as Castiel and sends Dean to 1944 to the fated submarine mission that sunk the Hand of God. Meanwhile, continuing his charade with Sam while they wait for Dean’s return, Lucifer plans his next move.
Dean sees an obituary notice for a wrestler he and Sam used to watch when they were kids. Deciding they need a break from tracking the Darkness, the brothers decide to attend the funeral to pay their respects. The funeral is full of wrestlers, including Shawn Harley, a hot shot new wrestler with a fiery temper who pushes everyone’s buttons, and veteran wrestler Gunner Lawless. Sam and Dean attend the next match to re-live one of their fondest childhood memories but when another wrestler turns up dead, play time quickly turns to work.
A dangerous creature is accidentally released into an old house, attacking a mother and her child, leaving them both in a coma. Sam and Dean learn that Bobby and Rufus once tracked the same entity so the Winchesters look to the past to come up with a plan to catch the monster before any one dies.
Sam and Dean battle a pair of werewolves who have captured two victims. Just as the brothers are about to win, one of the werewolves shoots Sam. Dean gets his brother and the victims out of the house but learns a pack of werewolves are hot on their tail, hoping to kill them all.
Lucifer takes a trip home and tries to assert himself into Heaven. Crowley tells Sam and Dean he has a way to take down Amara.
In a small town in Colorado, mysterious disappearances happen every 27 years. Sam and Dean head to the town to investigate and meet two hunters who have a personal vendetta against these once-in-a-generation monsters.
Amara unleashes a dark fog on a small town, causing everyone to go mad. Dean and Sam realize this is a stronger version of the original black vein virus Amara previously unleashed. They team up with the sheriff to protect the town but their old remedy no longer works. Meanwhile, Chuck returns with an interesting proposal.
Amara shows Dean how she’s torturing Lucifer. Worried for Castiel, Dean and Sam come up with a plan to rescue him from Amara’s clutches.
Sam and Dean face their biggest challenge yet. Rowena makes her move.
Dean is overwhelmed as he comes face to face with his mom, Mary Winchester. Meanwhile, Sam is fighting for his life after Toni, from the Woman of Letters, shot him.
Dean, Castiel and Mary have a lead on Sam and set out to rescue him. Dean is uncomfortable with putting Mary in danger but she insists on going along. Meanwhile, Crowley is tipped off that Lucifer has taken over the body of rock star Vince Vicente.
When a crying baby leads to death in a mysterious abandoned house, Mary, Sam and Dean decide to investigate. Meanwhile, Castiel’s hunt for Lucifer leads him, begrudgingly, to partner up with Crowley.
Sam and Dean investigate a case that leads them to a devout religious family that lives off the grid. The brothers realize that the parents are hiding a huge secret that could destroy them all. Meanwhile, Dean struggles to accept Mary’s latest decision.
After learning that the soul of Adolf Hitler has been trapped in a 1930’s gold pocket watch, Sam and Dean must act quickly to prevent a group of Nazi necromancers from resurrecting the Führer.
When hunters gather together to celebrate the life and tragic death of one of their own, Sam, Dean, and Mary must take action when a demon starts picking off hunters one by one.
Lucifer realizes that as rock star Vince Vincente, he can get his fans to do whatever he wants. Thrilled with this power, Lucifer arranges to play a secret VIP concert in order to kill all of them. Sam, Dean and Castiel enter the underbelly of the music industry to try to stop him.
Lucifer’s search for power and influence in a vessel lands him in the White House. The President of The United States unknowingly makes a deal with the devil, leading Sam, Dean, Castiel, Crowley and Rowena to band together to fight the Dark Lord.
After being arrested for the attempted assassination of the President of The United States, Sam and Dean must find a way out of an underground, government-run, detention facility in the middle of nowhere. Determined to find her sons, Mary and Castiel seek assistance from an unlikely source.
Lily Sunder steeps herself in black magic, honing her powers for over a century, waiting to exact revenge on a band of angels that murdered her family. Sam and Dean must work quickly to stop Castiel from becoming her next victim.
Sam enlists Rowena’s help to track down an old world, powerful family of witches after Dean gets hit by a spell that is rapidly erasing his memory.
Mary asks Sam, Dean and Castiel for help on a case she’s working but neglects to mention the British Men of Letters are involved. When Mary is double crossed, everything is revealed.
When Sam and Dean look into a murder at a museum, they learn a ghost from a merchant ship that sunk in 1723 may be at the heart of the mystery. After realizing “The Star” was the same ship that Crowley’s son Gavin McLeod should have been aboard, they enlist help from Rowena to track Gavin down. Kelly Kline, still pregnant with Lucifer’s child, takes refuge with a demon after an angel attempts to kill her.
A chance to take out a nest of vampires backfires when the alpha-vamp shows up and turns the tables on Mary and The British Men of Letters, who are doing their best to recruit Sam and Dean.
An attack by an invisible hellhound at a campsite leads Sam and Dean to investigate the mysterious circumstances. Meanwhile, two of Crowley’s own personal demons uncover what he has been hiding. Castiel gets a lead on Kelly Kline.
Sam and Dean let Mick Davies tag along on a case as they search for a werewolf. The three men run into Claire Novak, also working the hunt. However, the reunion is short lived after Claire is bitten and the brothers race to find a way to help her before she turns.
Sam and Dean get a lead on Kelly Kline’s whereabouts. Mick drops by the bunker unexpectedly and decides to join the hunt.
Sam and Dean investigate a missing person’s case in a small town. The lead witness tells the Winchesters the attacker was a man with the head of a goat. Sam and Dean aren’t sure what to believe but when the witness goes missing they realize the town is hiding a dark secret.
Sam comes up with a way to stop Lucifer’s baby but Castiel has something else in mind for Kelly. Dean is furious when he finds out someone stole the colt. Kelly makes a bold choice about the baby’s future.
Alicia Banes calls Mary for help after her mother, Tasha, goes missing. Sam answers Mary’s phone and he and Dean head out to help Alicia and her twin brother, Max, find their mother who was hunting a powerful witch. Meanwhile, Mary starts to have some doubts about the British Men of Letters.
Sam and Dean are alarmed when they learn hunters are being killed by suspicious “accidents” all over the country. They decide it is best to find Mary and make sure she’s safe. Meanwhile, Toni is back in the states and she and Mary face off.
Caught in a dangerous situation, Sam and Dean only have each other to rely on. Meanwhile, the fight between the American Hunters and the British Hunters comes to a head.
One Year Later Dean’s escaped from Purgatory, though Castiel is nowhere to be found. However, Dean isn’t alone. He’s returned with a mysterious comrade-in-arms whose reason for escape is perhaps more than Dean bargained for. Meanwhile, Sam finds himself reconciling the life he discovered while Dean was gone with Dean’s sudden reappearance. As the boys struggle with their unexpected reunion, they make a shocking discovery that could lead them on a deeply personal mission to settle old scores. If only they could agree – is this a “family business” or isn’t it?.
Kevin talks Sam and Dean into checking in on his mother. When they arrive, they see that Crowley has surrounded her with demons so they rescue her and take her along on their quest to find the tablet. However, they soon discover Kevin wasn’t kidding when he said his mother was a strong-willed woman after she tries to take on Crowley.
Sam and Dean investigate a string of unusual murders where the victims were all recipients of organs from the same donor. The killer is captured, but things become even more complicated when the brothers find their killer in a trance mumbling an ancient prayer.
Sam and Dean investigate a bizarre murder in a college town. Close on the tail of their suspect, they bust into an apartment to find two dead bodies and a laptop cued up to some disturbing video footage. The footage begins with Brian, Mike and Kate hearing about an unusual animal attack in their town and the rest of the story is revealed through their eyes. Sam and Dean become unknowing participants in a unique student film.
After Benny gets brutally beat up by some vampires, he calls Dean for help. Dean abruptly packs up and tells a confused Sam that he’s taking a "personal day." Benny confesses that he’s going after his Maker so Dean offers to help, flashing back on the many times Benny helped him and Castiel in Purgatory. Meanwhile, Sam uses his solo time to reflect on the life he left behind with Amelia. However, when things go bad for Dean and Benny, Dean calls Sam for help, which makes everything very complicated.
Sam and Dean investigate a murder and find Garth is already on the case. Dean is not happy to learn that Garth has assumed Bobby’s duties, but Garth points out that both Sam and Dean have been missing for the last year and someone needed to do it. They guys discover an "avenging ghost" is responsible for the murders and they need to find the source before the killings starts again.
Sam and Dean are stunned when Castiel suddenly appears back on Earth with no memory of how he escaped from Purgatory. Meanwhile, Mrs. Tran enlists a witch to concoct a demon bomb, but the witch double crosses Mrs. Tran and turns her and Kevin over to Crowley.
Sam asks a hunter named Martin to keep an eye on Benny without telling Dean. However, when Martin tells Sam there was a vampire kill and he thinks Benny is responsible, Dean defends his friend. When Martin decides to take things into his own hands, things get messy and Dean is forced to make a very hard decision.
Naomi tells Castiel that Crowley is holding an angel captive and Castiel must rescue him before Crowley finds out their secrets. Castiel turns to Dean for help. Meanwhile, Sam meets with Amelia who asks him to make a choice: stay with her or leave and never contact her again.
Sam and Dean investigate the mysterious deaths of two LARPers (Live Action Role Playing) who were playing a game entitled Moondoor. The guys are thrilled to discover the Queen of Moondoor is none other than Charlie. The three learn that a fairy has been commandeered to harm people and the only way to stop her is to find her master.
Sam and Dean are stunned when a man who claims to be Henry Winchester, their grandfather, suddenly appears in their hotel room demanding to know where he can find John Winchester. Henry has time-traveled to stop a demon named Abbadon and was looking for John’s help. Through Henry, Sam and Dean learn more about their father and the Winchester blood line.
Sam and Dean investigate the death of Rabbi Bass, who spontaneously combusted. The case becomes ever more confusing when they learn that the Rabbi was researching Nazi Necromancers. Sam and Dean are attacked by a Golem who turns out to belong to the Rabbi’s grandson, Aaron. The key to the case lies with the Golem but Aaron doesn’t know how to control him, which leaves everyone in danger.
Kevin deciphers the tablet and figures out how to close the gates of Hell. He tells Sam and Dean that according to the tablet one person must face a series of three tests designed by God. The first one – kill a hellhound. Sam and Dean argue over who should complete the trials.
A police officer named James, who turned to witchcraft after working a case with Sam and Dean, is plagued by nightmares in which he murders innocent people. However, when the murders actually happen, Sam and Dean are called in by James’s "familiar" to help -- but the brothers aren’t sure they want to save a witch.
Sam and Dean are stumped when they investigate a possible zombie case where an amnesiac man dies and then revives himself once a day. After the guy is attacked by the goddess Artemis, Sam and Dean realize he’s not a zombie but instead a God, more specifically, Prometheus.
Castiel reappears in Sam and Dean’s life and tells them Crowley has unleashed several demons into a small town. The demons are looking for Lucifer’s Crypt, which holds a valuable asset, but Castiel lies to Sam and Dean about what it is. While interrogating a demon, the three discover Crowley has been torturing Meg, who knows the exact location of the crypt. Sam and Meg fight to hold Crowley off while Dean and Castiel go in search of the crypt.
Sam and Dean investigate some recent vampire kills and are surprised to learn Krissy Chambers is involved. They find Krissy and learn her father was killed and she’s been taken in by a man named Victor, who has taken in a group of orphan kids to teach them how to hunt. Victor is helping the teenagers find the vampires who took their parents so they can get revenge. Sam is intrigued by Victor’s method of giving the teenagers a home life as well as a hunting life, but Dean is suspicious of Victor’s motives.
Sam and Dean respond to a call from Kevin, who is terrified after hearing Crowley's voice in his head. After hearing Kevin's news, Sam and Dean team up with a reaper named Ajay, who helps them deal with the second trial from the Tablet. Meanwhile, Dean receives a visit from Naomi and realizes he must find Benny and ask for a huge favor.
Concerned about the physical toll the second trial took on Sam, Dean benches his brother from hunting until he heals up. So, when geektastic hacker Charlie stumbles upon a case and finds the boys, Dean decides it's time to teach Charlie how to be a hunter-in-training. While happy to see "her highness," the boys suspect Charlie is hiding something; a secret that could get her killed.
When Sam and Dean receive a distressing video message from Kevin Tran, they set about trying to uncover the Third Trial. The boys make a discovery that sends them to a casino in Colorado, to find a mysterious recluse who may be able to fill in the holes in Kevin’s research. Meanwhile, Crowley is on a winning streak. Castiel tries to elude Naomi and the angels hunting him.
Sam and Dean reunite with Castiel. Digging through the Men of Letters' files, they stumble upon an undiscovered film which could be the key to the third trial. Metatron enlists Cass to mull over problems at home. Meanwhile, Crowley digs into Sam and Dean's past.
With Crowley poised to undo all the good they’ve ever done as hunters, Sam and Dean find themselves cornered. But with Kevin's help, the Winchester brothers bound into one last play against The Demon King. Metatron initiates a plan with Castiel to take on Naomi and the bureaucracy of Heaven.
After a ballerina is found dead from dancing herself to death, Sam and Dean look into the case and discover the ballet slippers she wore were cursed. When Dean accidentally touches the shoes the power of the curse starts to take hold of him.
Lucifer drives Sam to the breaking point and Sam ends up in a mental hospital. Desperate to save his brother, Dean calls every hunter he knows for help. One of the hunters gives him the name of a healer who turns out to have a very familiar face.
Dean is surprised when he gets a call from Garth asking for the brothers’ help on a case. Sam and Dean discover they are battling a Shojo, a Japanese creature sent to seek revenge on enemies. The worst part about fighting a Shojo? You can only see it when you’re drunk.
Sam and Dean get a call from Annie Hawkins, an old hunter friend, asking for help on a case. When they arrive in town, they find out Annie has disappeared. They trace her last whereabouts to an old abandoned house that is haunted by a powerful ghost.
Dick Roman acquires Frank's hard drive that contains sensitive information about the Winchesters and gives it to an unsuspecting brilliant hacker named Charlie telling her she has 3 days to crack the encryptionl or she is fired. Sam and Dean are tipped off that Dick has the hard drive and race to get to Charlie before she breaks the code. Meanwhile, Bobby tries to help the brothers, but his rage towards Dick for killing him starts to get in the way.
Meg calls Dean and Sam and tells them Castiel is awake and talking. Meanwhile, a teenager named Kevin gets hit by a bolt of lightening and is turned into a reluctant prophet. Sam and Dean believe Kevin holds the key to defeating the Leviathans but must fight off two Archangels who want him for their own purposes.
In order to defeat Dick Roman and the Leviathans, Sam and Dean must locate three key items. Castiel helps with one but for the last objects, the Winchesters must face two of their strongest opponents - an Alpha and Crowley. Meanwhile, Bobby tries out a new ghost trick that ends up being very dangerous.
Dean and Sam prepare for battle with Dick Roman. Dick's in the final phase of his plan and the Winchesters must team up with Castiel, Bobby, Meg and Kevin, the prophet, to stop him. However, Dick is one of the smartest enemies they've ever faced so it's a mind game to see who can keep the upper hand.
Dean is frantic after Sam collapses and the doctor tells Dean his brother won't make it. Desperate, Dean sends out an all points bulletin via prayer to every angel in the area, asking them to help his brother. In exchange, Dean will owe that angel a favor. Numerous angry angels race to find and kill Dean, but one, Ezekiel, gets to him first. Meanwhile, Sam fights for his life and must face some familiar demons to do so. Castiel struggles to survive without powers.
Dean shocks Sam by popping open the trunk of the Impala and showing him that he has kidnapped Crowley. Kevin freaks out when he sees the King of Hell, but Sam and Dean convince him that they need Crowley to find the demons on Earth. Meanwhile, Abaddon re-emerges and plans to take over Hell.
Ezekiel tells Dean a group of angels is hunting Castiel. Dean and Sam race to find their friend before the angels do. Meanwhile, a homeless Castiel is trying to make his way through the city and comes across some unexpected surprises.
Sam and Dean discover that the table in the Men of Letters house (the one that lit up like a Christmas Tree when the angels fell), has an ancient computer attached to it. They figure if they can get the computer on, they can track the angels. Who better to call for help than the best IT girl there is, Charlie? While moving the massive computer, they dislodge a hidden hexbag that unleashes a magical green-webbed wall. Sam and Dean break through it and discover the one and only Dorothy from Oz. She had trapped herself and the wicked witch in the web years ago to stop the witch from finding the key that would open the gate that connected their world with Oz. With the wall broken, a massive and magical fight ensues that threatens to destroy the Men of Letters house.
While investigating two bizarre murders, Sam and Dean realize there is an eyewitness to both gruesome deaths - a German Sheppard. Anxious to find out if they are dealing with a witch, a skinwalker or other supernatural monster, the guys look up a spell that could let Dean "communicate" with the dog. Unfortunately, the spell comes with side effects that no one saw coming.
Castiel gets a job at a Gas-N-Sip and actually starts to enjoy life as a human. A headline in the local newspaper about some disappearances in the area catches his eye, so he calls Dean to help him investigate the case. Dean knows he needs to keep Sam/Ezekiel away from Castiel, so he tells Sam that he and Kevin need to stay and work with Crowley to decipher the tablet. Crowley agrees to help Sam and Kevin but in return he wants one phone call to hell.
Dean gets a call from an old friend named Sonny asking for help with a ghost. Sonny runs a home for delinquent boys, and Dean was sent there for stealing food when he was younger. Sam is stunned he never knew this about his brother and asks for more information, but Dean dodges his questions. Another murder occurs while Sam and Dean are at the house, so they scramble to find the culprit before anyone else dies. Meanwhile, Dean looks up an old girlfriend and recalls his time at the house.
Sheriff Mills calls Sam and Dean for help investigating multiple murders in her small town. Discovering all four victims belonged to the same church chastity group, Sam and Dean decide to infiltrate by joining the group themselves. When Dean disappears, Sam and Sheriff Mills realize whatever they are hunting has taken Dean too and team up to rescue him.
After a massive angel slaughter occurs, Sam and Dean arrive at the scene to investigate and are surprised to run into Castiel. While investigating, Castiel is captured and tortured. Meanwhile, Dean questions Ezekiel's demands and wonders if it might be time to tell Sam the truth.
Dean is devastated after Kevin's death and vows to find the angel that killed him, not only to free Sam, but to seek revenge. Castiel arrives at the bunker and suggests they try to separate Sam's brain from the angel's so they can talk to Sam and have him expel Gadreel. However, there's one small problem: the only person who knows how to do that is Crowley.
Looking to reclaim his place as King of Hell, Crowley asks Dean for help finding "The First Blade," the only blade that can kill Abbadon. Knowing he owes Crowley a favor for helping Sam, and also wanting Abaddon dead himself, Dean reluctantly agrees and the two set off on a road trip. However, Dean and Crowley are completely unprepared when they find out who has the blade - Cain, the first son. Meanwhile, Sam is back at the bunker with Castiel who notices there is some leftover grace inside Sam. If they can extract it, they can use the grace to track Gadreel. The only problem is the procedure may do permanent damage to Sam.
After finding out that Garth is in the hospital, Sam and Dean go to check on him. Still carrying the guilt over Kevin, Dean lays into Garth about disappearing and demands to know where he's been. Garth makes an excuse and then hightails it away from the guys. Confused as to why Garth would run from them, Sam and Dean do some investigating and are stunned by what they find.
Sam and Dean investigate recent murders where the victims were hundreds of pounds lighter after their deaths. Suspecting witches, the two go undercover at a fancy day spa that all of the victims had attended for weight loss. While Sam is hired as a fitness instructor, Dean takes kitchen duty. After Dean swipes some tainted food and passes out, the guys realize someone is drugging the guests and literally sucking all of the fat out of them until they die.
Sam and Dean are stunned to discover the Men of Letters’ bunker is haunted. Their investigation leads them to a storage facility where the demons have been keeping a prize possession. Meanwhile, Castiel is captured by Bartholomew.
A teenage girl is killed and the final selfie she took before the attack shows a ghostly figure in the background. Looking for something to keep them busy, Dean and Sam head to Washington to find the ghost. While the two interview the girl’s mother, Betty, they are surprised when she starts talking about cold spots and fritzing. When they ask her about bringing up paranormal signs, Betty replies that the "supernaturalists" who called earlier brought it up. Enter Harry and Ed, the famous supernaturalists.
Dean is frustrated when he can’t reach Crowley, who has promised to find The First Blade. When Crowley finally calls Sam and Dean, he tells them he fell off the wagon and has been injecting human blood and needs their help. To make matters worse, he had a demon helping him find blood, but she sold him out and told Abaddon that he and the Winchesters were searching for The First Blade. The brothers need to find the blade before Abaddon does, so they enlist the help of a former member of the Men of Letters.
Dean struggles with the after effects of the Mark of Cain. Meanwhile, Sam hears about a case where straight-laced people are turning into violent murderers. Sam suspects possession and suggests to Dean that they investigate, but Dean tells him to go without him. While interviewing the local townsfolk, Sam meets an elderly woman named Julia, who tells him the Men of Letters came to town in 1958. Josie tells Sam the story of a young man named Henry Winchester and his female companion, Josie Sands. While Sam is away, Crowley tests Dean.
Metatron attempts to get Castiel to join forces with him. Still furious with Metatron, Castiel refuses, which sets a surprising plan in motion. Meanwhile, Sam and Dean capture Gadreel.
Sheriff Mills calls Sam and Dean after she kills a vampire who attacked a prisoner named Annie. They discover Annie was kidnapped by a family of vampires who use her as bait to lure in humans they can then feed on. Sheriff Mills tries to rescue Annie from her captors, but finds out the hard way that family always comes first.
Sam and Dean investigate a case in Chicago, where they discover that various mafia-esque monster families are, unknown to humans, running the underbelly of Chicago. One is a family of shapeshifters run by Margo Lassiter, whose leadership is thrown into question when her brother David returns home. The other reigning family in town is made up of werewolves, lead by Julian Duval. While in Chicago, Sam and Dean meet Ennis, a man with a personal vendetta against the monsters. The Winchesters warn Ennis about heading into the hunter lifestyle, but Ennis refuses to listen and starts down a dangerous path.
Castiel captures one of Metatron’s angels and asks Sam and Dean for help with the interrogation. Dean eagerly accepts, which doesn’t go unnoticed by Sam. Meanwhile, Abaddon demands Crowley help her kill Sam and Dean. When he refuses, she reveals her shocking bargaining chip. Also, Castiel sets a meeting with Gadreel.
After a massive attack on the angels, Castiel calls Sam and Dean for help. As they leave, Dean’s eagerness to bring the First Blade doesn’t go unnoticed by Sam who is worried about the cost to his brother whenever he uses the Blade. Meanwhile, Castiel is shocked when he learns the angel that caused the attack was one of his followers and did it in his name. Dean discovers there is a conspiracy amongst Castiel’s angel followers and at the heart of it is Tessa, the Reaper.
Dean feels the effects of the First Blade, and Metatron makes his move against humanity. Meanwhile, Sam, Dean and Castiel face shocking consequences when taking the fight to Metatron.