Finch goes under cover to protect a youth who reminds him of himself; Carter goes on a dangerous mission for the FBI.

Finch infiltrates a tech corporation to gather intel on an executive whose number has come up; Carter questions Beecher's integrity.

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.

Finch goes undercover in an emergency call center to protect a 911 operator, but it soon becomes clear that the threat reaches further than the team could have anticipated.

As Decima uses Samaritan’s feeds to hunt Reese and Shaw, Greer exploits Finch’s greatest weakness in an attempt to lure him out of hiding: his love for his former fiancée, Grace Hendricks.

Despite not wanting to help with the new numbers, Finch's interest is piqued when the newest person of interest turns out to be a brilliant college student involved with a mysterious scavenger hunt.

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.

Finch and Root race to save The Machine, which has been located by the rival AI, Samaritan. Also, Reese is caught in the middle of the final showdown between rival crime bosses Elias and Dominic.