The Doctor escapes from the Sarah android. Styggron and Chedaki now set their final phase in motion: the destruction of the training village and the Doctor with it. They will then be ready to invade Earth, using a virus to wipe out human life. Styggron wants to test the virus on a living human.
The robotic guards gather up the villager androids and bring them to Styggron's ship. Sarah manages to evade the others and escape into the village.
Styggron captures the Doctor in the village. He has the guards tie the Doctor to the town monument and sets a bomb to destroy the training ground. Sarah then emerges and cuts the Doctor loose. They flee into Styggron's ship just ahead of the explosion but are captured by the androids and imprisoned. Styggron wants to kill them, but Crayford persuades the Kraal to spare them for analysis.
The Doctor tells Sarah the Kraal planet is becoming uninhabitable due to radiation and they have been using the village to train androids for an invasion of Earth. Crayford overhears and tells them the rest. He has been in contact with Earth and will soon return, bringing the invasion force with him. He explains that he is helping the Kraals because his ship was damaged and adrift and the Kraals saved him. He has been promised that no humans will be harmed if they let the Kraals occupy part of the planet but the Doctor is sceptical.
Styggron has the Harry android prepare the virus for testing on Sarah. He contaminates a jug of water and takes it to the prisoners.
The Doctor opens up a floor panel to reveal a power line that could be used to disable the android guard. He is taken away for examination but persuades Sarah to save the poisoned water for use against the androids.
The Doctor is taken to the theatre and strapped in. Styggron sets the machine and leaves it to copy the Doctor's mind and then destroy him.
Sarah sets her scarf on fire to bring the guard into her room, then shorts him out with the power line and water. She frees the Doctor before the machine can kill him. They then race to Crayford's ship, which is about to launch. The Doctor manages to get Sarah into a capsule to protect her from the force of the launch but he falls to the ground as the rocket blasts off…