John Reese, a presumed dead former CIA agent who is approached by a mysterious billionaire named Harold Finch to prevent violent crimes before they happen by using an advanced surveillance system dubbed "The Machine". Their unique brand of vigilante justice attracts the attention of two NYPD officers, Joss Carter and Lionel Fusco, whom Reese uses to his advantage as he investigates persons of interest. Reese and Finch are later aided by Samantha "Root" Groves , a highly intelligent computer hacker and contract killer who the Machine later identifies as its "analog interface" and Sameen Shaw, a former ISA assassin who unknowingly dealt with the "relevant" numbers found by the Machine.
Finch tries to protect a 911 operator by going under cover in an emergency call center; the threat proves to be larger than anticipated.
Secrets of Finch's pre-Reese operation are revealed -- including surprising ties to current events.
The Machine assigns Root to seek out a janitor with a mysterious past, but when her very presence puts his life in danger, Finch also receives his number.
When Reese and Finch have to protect a former government contractor who is following a UN diplomat, they are thrust into the murky waters of international politics.
In order to protect the latest person of interest, Shaw and Reese go under cover at a high school reunion; Fusco and Finch go to Washington, D.C., to investigate Vigilance's most recent attack.
Reese goes under cover as a secret service agent in order to get close to the latest person of interest, a congressman who may have the key to derailing Decima's plan for a second machine.
Reese and Shaw are hunted by Decima; Greer uses Finch's greatest weakness -- his former fiancee -- to lure him out of hiding.
The machine sends the team five different numbers to investigate when an unknown entity blocks details about an impending catastrophic event; Root's hackers arrive in New York.
The team work to stop Samaritan from coming online and targeting them; the battle against Vigilance reaches a conclusion.
Reese and Shaw struggle to find a naval officer among all those in town for Fleet Week; Carter puts a plan in motion to get rid of those who set her up; Root tests her new surroundings.
Reese tries to protect an Internet entrepreneur who targets people's privacy; Carter is paired with a rookie partner.
Finch and Reese ask Zoe Morgan, Carter and Shaw to help them determine if a playboy is a predator or a target; Root plots an escape from the psych ward with the help of the machine.
The team must figure out if a prominent lawyer orchestrated the murder of her husband or if she is being framed; Carter is spotted with Reese by her new partner.
Shaw must stay close to a 10-year-old girl with highly developed surveillance skills when she is identified by the machine; Carter's mission could be exposed.
After being freed from her confinement to the psych ward, Root needs Shaw's help with a directive from the machine; Finch and Reese look into a mild-mannered investigator.
The team is met with surprises during an investigation into a hypnotherapist; an antiquities dealer has ties to a crime organization.
The machine gives Finch 38 numbers at once; information about Carter's past is revealed.
The battle to bring a crime organization to justice reaches a new level; Reese's number comes up in the machine.
As the team seeks justice for a death, Finch fears one team member will go too far; the number of one of HR's key players comes up in the machine.
Flashbacks reveal Finch's creation of the machine; Reese hits the road, leaving the team to deal with the aftermath of their war with HR.
Multiple enemies target the team as they try to protect a dying man; Reese's absence could lead to catastrophic repercussions.
Reese gets on an international flight -- intending to leave the team and the past behind -- but realizes his travel plans were manipulated.
Reese comes back to New York; surprising events lead to the team planning a heist that could send them all to jail.
In the fourth season premiere, the team must devise new ways to continue their work without being detected by Samaritan after they're forced to take on new identities created by Root. Some, however, find it hard to ignore the Machine's numbers, putting them all at risk of being seen by the rival machine.
Although Finch insists that he no longer wishes to help with new numbers, his interest is piqued when Reese learns that the newest POI is a brilliant college student engaged in a mysterious, life-and-death scavenger hunt. Now he must decide if he can help without alerting Samaritan.
Finch recruits Fusco to stay close to the latest POI, a professional "wingman" whose number has come up, but learning how to approach women soon becomes the least of his worries. Meanwhile, Reese must find a way to play by the rules at his new day job as the Machine sends Finch and Root on a mysterious errand.
Reese's cover job as an NYPD detective becomes complicated when the young brother and sister he's protecting become targets of a gang investigation.
Finch is suspicious when a gifted political pollster's number comes up at the same time that his typically ironclad predictions go wrong – and believes that the two events are linked. Meanwhile, Reese is sidelined by a direct order from Captain Moreno. Jason Ritter guest stars as pollster Simon Lee.
Reese, Shaw and Fusco must protect an unassuming office worker who stumbles into a dangerous conspiracy while moonlighting as fake detective. Meanwhile, Finch travels to Hong Kong as part of his academic cover identity.
Shaw joins a team of international thieves in order to keep tabs on the latest POI, but an unexpected turn of events puts her in danger of being detected by Samaritan. Finch and Root, meanwhile, undertake a dangerous sabotage mission.
Reese volunteers as an NYPD police academy instructor in order to keep an eye on a talented young officer whose suspicious actions make him question her motives. Meanwhile, Martine – armed with information from Samaritan – hunts a member of the team.
Reese must save Elias from the Brotherhood. He can't get any help from Root or Shaw since Shaw's cover is blown and Root is escorting her to underground.
Samaritan demonstrates its true power by taking control of New York for 48 hours and erasing crime from the city in an attempt to lure The Machine out of hiding.
Samaritan launches a cyber-attack on the stock exchange, forcing the team to risk their lives in a desperate mission to stop a global catastrophe.
Control, who oversees the handling of relevant numbers for the government, begins to question the methods and intentions of the Samaritan program. Root and Reese start looking for Shaw, whom they believe is still alive.
Root and Reese’s hunt for Shaw takes them to a small town in upstate New York where it becomes apparent that not everything is as idyllic as it seems. Also, Fusco teams with a former POI to tackle the newest number.
When the Machine arranges for Finch to sit on the jury of a murder trial, he begins to suspect that a fellow juror is set to rig the proceedings. Meanwhile, Reese begins to open up to the department’s therapist.
Reese tries to protect a software programmer with a mysterious second life, but it’s unclear which side of her life the threat is coming from. Meanwhile, Claire, a young hacker whom Finch tried to protect from Samaritan, reaches out to him for aid.
Reese and Finch must protect Harper, a street-smart grifter, when her plan to steal cash from a medical marijuana dispensary goes up in smoke.
Reese and Finch try to protect a psychologist whose unorthodox methods for helping his patients find closure could cost him dearly. Meanwhile, flashbacks reveal Finch’s fragile state in the days following the bombing that killed his best friend, Nathan Ingram.
Reese must protect a bounty hunter who refuses to let the potential threat to her life deter her from the relentless pursuit of her target. Also, Finch tries to set the plan he began in Shanghai in motion.
Reese and Finch scramble to protect a software CEO when his behavior becomes increasingly erratic following a hacker attack that reveals all his secrets and unravels his life.
Reese finds himself on a perilous personal journey when he takes on a homicide case Detective Carter was never able to close.
Reese and Fusco get caught in the war between the two newest POIs, rival crime bosses Elias and Dominic. Also, a tantalizing clue to Shaw’s whereabouts leads Finch and Root into a possible trap, and Control goes rogue to uncover the true intentions of the Samaritan program.
Reese and Finch attempt to rescue the Machine’s source code before it deteriorates beyond repair. Also, Root fights for her life against an onslaught of Samaritan’s agents and Fusco is faced with hard questions following the deaths of Dominic and Elias.
The Machine experiences a glitch during rebooting, supplying Reese and Fusco with the numbers of dozens of people not actually involved in crimes, while also locking Finch and Root out after identifying them as threats based on past violent behavior.
Reese’s cover could be blown when he realizes the latest POI has ties to his old CIA colleague, Kara Stanton.
Sameen Shaw escapes her captors, but the team is unsure of her mental state when she begins to act paranoid and reckless.
Reese protects an NYPD analyst whose investigation into a software glitch has drawn the attention of Samaritan. Also, Reese and Fusco are threatened by an ally of Elias’s, who is looking to avenge his friend’s death.
The Machine sends Reese and Finch to a wedding to protect a pair of POIs before their nuptials. Also, Fusco becomes angry at being kept in the dark by the team and takes it upon himself to investigate a string of missing person reports.
Root goes undercover at a radio station to protect the host of a conspiracy theory show who stumbles upon information that could get him killed. Also, Samaritan’s agents try to convince a member of the team that their goals are noble.
Reese and Finch become trapped in a hospital that becomes ground zero for a deadly viral outbreak. Also, Samaritan’s newest recruit has second thoughts and Shaw continues to struggle with reality.
The mysterious criminal mastermind known as “The Voice” returns and traps Reese and Fusco in their own precinct with several armed gang members and the latest POI. Also, Root makes a shocking discovery.
Finch’s number comes up when a fatal error blows his cover identity and sets off a deadly series of escalating encounters with Samaritan’s operatives.
The team must unravel a conspiracy and stay ahead of the Secret Service when the President of the United States becomes their newest POI. Also, Finch separates himself from the team and considers taking drastic action to combat Samaritan.
As Reese and Shaw race to catch up with Finch, he infiltrates a maximum-security government facility in a desperate mission which could mean the end for not only Samaritan, but for himself and The Machine as well.
Reese and Finch are puzzled when the machine names a 6-month-old baby as the latest person of interest; Detective Carter questions her allegiances when Elias resurfaces.
The Machine's latest number presents a unique challenge for Reese and Finch since the person has virtually no digital footprint - and appears to be leading a double life.
When The Machine spits out five numbers, naming the Don of each of New York’s crime families, Reese and Finch suspect Elias is planning to eliminate his competition.
To track the latest person of interest, Reese goes under cover as part of an armored truck crew; throughout the case, Reese is reminded of tough decisions he was forced to make during his last CIA mission.
A person of interest winds up in the middle of a dark government conspiracy that Finch is all too familiar with; Reese makes a discovery about Finch's past.
The Machine leads Reese and Finch to Wall Street when a sharp young trader at a major investment bank becomes embroiled in a multi-million dollar financial scam.
On Reese's birthday, Finch gives him the day off in hope of keeping him away from the latest person of interest.
Reese asks Detectives Carter and Fusco for help finding Finch, who was kidnapped by his nemesis.
As Reese investigates a cold case, he gets closer to Finch and his kidnapper, Root.
Reese protects the spoiled daughter of a Brazilian diplomat.
Reese and Finch wonder if they should intervene when they learn that a mob enforcer's life is in danger; Finch turns to an unexpected source for help.
Reese must surreptitiously protect an investigative reporter without becoming a part of her story.
The Machine’s latest number sends Reese to the suburbs.
A resourceful third party raises the stakes as Finch and Reese try to protect their latest person of interest, a brilliant surgeon.
The team faces a challenge when the numbers of both a man and his wife come up in the machine.
When the machine names a New York cabdriver as a person of interest, any of his passengers could be a part of the impending crime.
As the FBI pursues "the man in the suit," Reese is even more determined to protect the latest person of interest after learning she is the sister of a soldier who was killed in action.
Finch goes under cover to protect a youth who reminds him of himself; Carter goes on a dangerous mission for the FBI.
Carter tries to help Reese by engaging in mental warfare with the FBI; Reese has encounters with old and new enemies; Detective Fusco must protect supermodel Karolina Kurkova, the latest person of interest.
Reese is captured by a former acquaintance planning a massive and potentially deadly act of cyber-warfare.
Finch and Reese meet their match: a tech billionaire whose curiosity and endless resources could expose their identities and ruin their efforts to save his life.
As Reese and Finch try to save a hotel maid's life, they encounter a litany of suspects; Detective Carter considers a significant offer from the FBI.
The latest POI - a deadly government operative who tackles terrorist threats - proves difficult for Reese and Finch to protect.
As Finch and Reese try to protect six people simultaneously, clues lead them to a coastal town; when a storm forces Finch and Reese to seek shelter in a police station with a group of locals, they realize a killer may be in their midst.
Finch and Reese head to Atlantic City to protect the latest person of interest, an elderly gambler; Carter tries to clear another detective's name.
Finch infiltrates a tech corporation to gather intel on an executive whose number has come up; Carter questions Beecher's integrity.
When a person of interest is poisoned, Finch and Reese only have 24 hours to identify the toxin and find the person responsible; Detective Fusco's past catches up to him.
When a virus causes the machine to malfunction, numbers are issued irregularly; the team searches for an extremely elusive tech millionaire.
Finch and Reese team up with unexpected allies as they race to fix the machine; as Detective Carter tries to apprehend Cal Beecher's murderer, she finds herself up against HR -- a criminal organization.