Jim Phelps: Peter Graves
Paris: Leonard Nimoy
Dana Lambert: Lesley (Ann) Warren
Barney Collier: Greg Morris
Willy Armitage: Peter Lupus

Werner Stravos: Bruce Glover
Eric Bergman: Albert Paulsen
Valerie: Jessica Walter

Werner Stravos is an enemy assasin, but no photographs of him exist. The IMF can only work on little information to save the next victim. Stravos gets his orders from an unknown member of the "central committee" and is to kill the next victim in two days at 4 o'clock. They also know that Eric Bergman is the only contact man to him.

Now Jim poses as a heroin addict who has "killed" Willy. This forces him to change to "the other side". The "other side" puts him on withdrawal and learns from Jim that there is a double agent called "Orpheus".

Meanwhile the IMF arranges papers for Valerie to enable her to be accepted as an official officer from that group. She leads a tough interrogation on Paris. During the interrogation the lie-dectector clearly states when Paris is lying. Thanks to Barney the machine always identifies a lie when Paris presses his ring-finger on a device connected to the machine. This is not noticed by the group interrogating Paris. Valerie's on the point questions reveal: Paris is identified as an agent, who one of Stravos' former victims believed dead. The others now strongly believe that Stravos must be the double agent.

Bergman now wants to meet Stravos. Stravos agrees. When he meets Bergman (Paris takes over) he tells Bergman where the next victim is to be murdered. The IMF saves the victim in time.