The Machine finally sends a Number to the undercover Reese and Sam, and Reese tries to convince Finch to help them. When he won't, Reese is forced to go it alone to save two lives.
Reese turns to a reluctant Finch for help with their new Number, a gifted mathematics student who is trying to win a bizarre urban game with a sinister ulterior motive. Meanwhile, Sam pursues her second career as a street thief.
Fusco goes undercover as a man desperate to get a date, so he can get close to the new Number, a professional wingman. Meanwhile, Reese tries to impress the new captain, while Root takes Finch on a scavenger hunt on behalf of the Machine.
When a young brother and sister witness a gangland shooting, they take a half million in drug money and go on the run. Reese goes looking for the team's two new Numbers and finds the Brotherhood after them. Meanwhile, Finch turns to Elias for help.
While Reese is forced to undergo therapy for his violent tendencies, Sam, Root, and Finch try to help a pollster who has run afoul of Samaritan.
An unassuming insurance agent becomes a private detective to investigate the apparent suicide of a co-worker's brother, but soon gets in over his head. Meanwhile, Finch travels to Hong Kong to present a paper.
Finch sends Sam in to infiltrate a gang of thieves whose leader is the team's new Number. Meanwhile, Root helps Finch undermine Samaritan's newest scheme.
Reese volunteers to teach at the police academy to keep an eye on the team's new Number, a recruit who is spying on her fellow classmates. Meanwhile, Mini launches his plan to get the information he needs to bring Elias down.
Reese and Finch find themselves involved in a power struggle for control of the city’s gangs after Elias becomes a target for Dominic, the leader of the Brotherhood.