This story introduced Zoe Heriot (Wendy Padbury) as a companion. Only the third and sixth episodes exist.
The tale begins with a re-cap of Victoria’s departure from the previous story. The TARDIS is marooned by technical problems on a deserted out-of-control spaceship. The only being on board, a servo-robot, detects them and re-directs the ship, causing the Doctor to hurt his head. Jamie destroys the robot, but the Doctor passes out. The robot has launched pods to a nearby space-wheel. Aboard the wheel, Controller Jarvis Bennet (Michael Turner) is about to destroy the wandering supply-vessel as a danger to shipping, when a deafening burst of noise is heard, which alerts them to the Doctor’s and Jamie’s presence aboard the ship, and they are rescued.
While the Doctor is being treated by Doctor Gemma Corwyn (Anne Ridler), Jamie is shown about the vessel by Astrophysicist/Librarian Zoe Heriot (Wendy Padbury). She knows that Jamie is lying about something. Bennet is about to destroy the Silver Carrier, as they call the roving ship, with the TARDIS on board, so Jamie sabotages the laser, leaving them all helpless before a possible meteor shower and causing further suspicion. Some of the pods attached to the wheel contain Cybermen. Cybermat creatures attack the ship’s bernalium, necessary for the laser. The Cybermen have engineered a nearby star to go nova. The Cybermats are discovered. Crewmen are sent to the Silver Carrier for bernalium and their minds are taken over by the Cybermen, who are brought aboard the wheel in shipping crates. Several crewmen are killed.
The Cyber-Planner recognizes the Doctor, who is warned by Jamie and Zoe. The Doctor electrocutes one of the Cybermen that come after him, then he and other crewmen destroy more Cybermen, including an entire army space-walking their way. The Doctor and Jamie return to the Silver Carrier with the materials needed to repair the TARDIS. Zoe stows away and comes with them as they leave.
The story was not liked by critics, who thought it dull and the Cybermen not very formidable, with a ridiculously complex plan that was hard to follow and harder to swallow. The spacesuits worn by Jamie and Zoe (high-altitude Windak pressure suits used by the RAF) also appeared in the first two Star Wars movies.