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.
In the Season Four finale, Finch and Root race to save The Machine, which has been located by its AI rival, Samaritan. Also, Reese is caught in the middle of the final showdown between rival crime bosses Elias and Dominic.
Reese and Finch must protect Harper (guest star Annie Ilonzeh), a street-smart grifter, when her plan to steal cash from a medical marijuana dispensary goes up in smoke. How many enemies can one person make?
When a starving toddler is found wandering the streets, detectives are led to a home where another child is in grave condition; Chief Dodds (Peter Gallagher) suggests that Benson's squad may be undergoing changes.