engineer called Dask stays behind to repair the damage to the controls. The Doctor and Leela continue to investigate the murders, with the Doctor convinced one of the robots is behind it. Leela takes him to meet D84, and D84 explains that he and Poul were planted on the vehicle as a precautionary measure against a robot revolution that may be initiated by Taren Capel, a scientist that had been raised by robots and with delusions of power. D84 joins them to search the vehicle, and they discover a secret laboratory where the other robots have been reprogrammed to kill humans. Suspecting that Taren is aboard, the Doctor requests all the humans to meet them on the bridge. Poul, however, having discovered a damaged robot in the repair shop with a bloody left hand, realizes that the robots are responsible for the murders, goes mad, and shelters in the shop. However, Dask refuses, and reveals himself as Taren; he shuts down all of the robots except those he had reprogrammed (excluding D84), and orders SV7 to start hunting down the remaining humans. As D84 retrieves Poul, the Doctor and Leela return to the robot repair section, and find the damaged robot with Borg's blood on it; the Doctor surmises that Borg had been strong enough to put up a struggle against his robot assassin, and that this discovery had driven Poul insane. The Doctor uses the spare parts to construct a deactivator that will shut down all robots in close range, and then instructs Leela to hide with a canister of helium gas to use when Taren returns. Taren is lured to the laboratory by the Doctor and D84, and D84 sacrifices himself to use the deactivator to shut down the Voc guard in the laboratory and itself. When SV7 arrives to kill the remaining humans, Taren begins to give SV7 orders to kill the Doctor, but the helium released by Leela causes Taren's voice to become high-pitched and unrecognisable by SV7. The Super Voc then kills him. The Doctor helps to shut down SV7 and revert Taren's programming. After ensuring that Poul and the others are safe and help is on the way, the Doctor and Leela take their leave. Production Early titles for the script included Planet of the Robots and The Storm-mine Murders. The treatment of robots in this serial has many intentional nods to Isaac Asimov's