Although they’ve saved countless lives thanks to The Machine’s omniscience, John Reese and Harold Finch, along with lethal operative Sameen Shaw and unpredictable cyber-hacker Root now face an uncertain future. With a second machine — Samaritan — now online, the elusive team are now targets themselves, hiding in plain sight. The only thing more frightening than the ruthless Decima organization calling the shots is leaving those decisions up to an untested Machine. Facing a dangerous tomorrow, the POI team must find a way to outsmart Samaritan, an all-seeing, all-powerful artificial intelligence that’s self-governing, continually evolving and growing stronger every day.
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 a 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.