When the social security number of a young prosecutor comes up, Reese and Finch work together to figure out if their person of interest is the victim or perpetrator.

Reese and Finch question the machine's reliability when they are asked to investigate a teenager who was killed years earlier; Finch remembers the origin of the machine.

Reese and Finch get some help from Detective Fusco as they surveil their latest POI, Dr. Megan Tillman, while she’s on call and after hours to unravel the threat surrounding the promising young physician.

When The Machine spits out the number of a 6-month-old baby, Reese and Finch turn into overly protective parents – with an arsenal at their disposal. Meanwhile, when Elias resurfaces, Detective Carter begins to question her new allegiance with Reese and Finch

Reese must protect an investigative journalist through surreptitious means to avoid becoming part of her story.

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.