On the season premiere of Person of Interest…
Reese and Finch get a number from the Machine about a sailor during Fleet Week.
Carter, now a beat cop, helps Reese find him.
Spec ops want the sailor and his buddy to return uncut diamonds they smuggled into the United States.
Root, called "Robin" in the psych ward, discusses her interactions with the Machine. The psychiatrist wants to disconnect her from all technology. Root reveals her argument with the machine is about whether or not she is going to kill the psychiatrist.
Carter, who helped Elias escape last season, meets with him to find out who would fence diamonds. Carter hasn't told Reese or Finch about letting Elias free. She also hasn't quit her war against HR.
After a shootout involving Spec ops and the Russians, Shaw and Reese help the sailor get out. Elias' man takes the diamonds and the money.