The F.B.I. begins its fifth season as Federal Inspector Lew Erskine (Efrem Zimbalist Jr.) persuades former counterespionage agent Anne Fraser (Diane Baker) to come out of retirement for one last assignment. Posing as lovers, Erkine and Anne hope to round up a spy ring specializing in blackmailing vulnerable diplomats--a task made difficult by the fact that the villains are protected by diplomatic immunity. In the original TV Guide ads for this episode, the producers shamelessly plugged their series' longtime sponsor by listing "The 1970 Fords" as "guest stars"!