A man holds Dr. Lightman hostage, claiming that he did not kill his wife and demanding that The Lightman Group help him find the killer.

An old friend from Lightman's past comes for help, and gets Lightman involved with a dangerous man being investigated by the FBI. Meanwhile, the rest of the team tries to find the high schooler behind a dangerous and threatening video.

Holder and Sarah get a break in the case; Seward clashes with death; Bullet becomes a protector.

Sarah goes missing; Bullet makes a choice to save Lyric; a dark secret is learned.

When the Machine directs Reese and Finch to a former soldier with shady connections to a crime ring, Reese must infiltrate the gang, taking part in their heist. Meanwhile, Detective Carter's closer than ever to finding out who Reese is.

When the number comes up on a promising young doctor, Megan Tillman, Reese and Finch must unravel the threat while she's on-call and after hours.

When the Machine produces the social security number of a judge renowned for his tough sentencing, Reese and Finch have the added challenge of investigating a person of interest who wants nothing to do with their brand of vigilante justice.

Former international CIA operative Wesley Cole returns home and becomes Murtaugh's partner on the force; Avery continues his campaign for city council.

Murtaugh and Cole try to find their stride as they work to solve the murder of a finance executive; Cole navigates his role with his ex, Natalie, and his daughter, Maya; Avery grapples with the outcome of his campaign for city council.