Another one of my recent Doctor Who purchases... Not much to look at yet, admittedly.
The Robots of Death is a classic Doctor Who serial from the Tom Baker era. Aboard a giant mobile mining vehicle largely staffed by humanoid robots, the Doctor and Leela have to solve a mystery - who is murdering the crew one by one?
D-84 is an intelligent detective, disguised as a "Dumb" class labour robot, put on board to protect the crew from the murderer. Eventually he sacrifices himself to save the doctor and remaining crew members.