V.4 tries to strangle the Doctor but Uvanov drives a Laserson probe into its head, "killing" it. Uvanov tries to remove the probe but V.4 revives and attacks him, damaging him. V.6 gets into Toos' quarters past the lock and advances on her. The Doctor escapes with the wounded Uvanov but V.4 pursues and they run into V.5 and SV.7. The Doctor uses his scarf t cover V.5 and V.4 attacks it. They escape, and SV.7 calls on V.4, who stops his attack on Toos and goes to help them.
Leela investigates and finds D.84 over Toos and attacks him, but he convinces her he's helping the Doctor. He goes to get Poul while Leela takes Toos to the command deck. Meanwhile, SV.7 sends the other robots out to kill the cool, and Leela and Toos have to take refuge in a hopper. The robots go away and Toos calls to SV.7, but Leela suspects something is up and tells Toos not to give their location away.
The Doctor and Uvanov get to the command deck where the robots have been deactivated. Leela and Toos arrive as does D.84 with Poul, who is still in shock. The Doctor confirms he had suspected Poul due to his body language, and he's suffering from robophobia. Uvanov reveals that the boy he left to die had suffered from robophobia and was force to leave him, and Zilda's father covered it up. SV.7 tells them to surrender or they'll be destroyed. The Doctor suggests they come up with anti-robot bombs from blast charges and goes to the robot mortuary with Leela and D.84.
On the Command Deck, the others hear Dask pounding on the door with the robots in pursuit. Uvanov tries to open the doors but Toos stops him, suspecting a trap. Outside it is clear that Dask (actually Capel) has now completely taken on the role of a robot, donning make-up and clothing. When his ploy doesn't work, he tells the robots to break down the doors.
While the Doctor explains what robophobia is to Leela, he take the communicator circuit out of an incapacitated robot and makes a "final deactivator" that will destroy the brains of all the robots. D.84 returns with a tank of helium the Doctor has sent for, and assures the Doctor he should use the deactivator if necessary.
On the command deck, Poul wakes up and sees V.5 breaking in through a side panel. The robot reports to SV.7 that the Doctor and Leela are no longer on the command deck and he leads the robots after them. Uvanov uses a blast charge on V.5 and manages to destroy it. Uvanov insists they go out and start hunting the robots.
The Doctor has Leela hide in a room and gives her the canister, saying it's helium that will alternate the resonance of Dask's voice so the robots won't recognize it. He and D.84 go out to look for Dask but the insane man drives the Laserson probe into D.84's head and knocks out the Doctor. Leela opens the gas canister while Dask straps the Doctor to a chair and prepares to use the Laserson probe on him. He slowly starts to burn out the Doctor's brain as his voice changes and the Doctor taunts him, stalling for time. Unseen by them all, D.84 makes a desperate effort to grab the abandoned Final Destructor and blow out the brains of the nearby robots, including himself.
As Dask tries to kill the Doctor, the remaining SV.7 comes in. Not recognizing Dask's altered voice, it kills him. Uvanov and Toos come in and SV.7 attacks them, but the Doctor destroys it with the Laserson probe. The Doctor lets out Leela, who has an altered vice as well. They quietly slip away from the others and leave in the TARDIS.