Release Message:  The Doctor (Tom Baker) starts looking into the possibility that the murderer is a robot, and another crew member is targeted for death.

Description:  As the strangulations continue and the humans aren't sure who to blame, Leela meets up with an anomaly among the robot crew - an inquisitive, supposedly mute single-function labor robot capable of independent reasoning. Meanwhile the Doctor starts looking into the possibility that the murderer is a robot, and another crew member is targeted for death.