have deliberately infected the ship and places the whole ship on alert. After a trial, during which Steven collapses with the fever, Zentos orders the execution of the Doctor, Steven and Dodo, but the ailing Commander intervenes to protect them and permits them access to medical equipment to devise a cure. The Doctor is able to recreate the cold vaccine from the membranes of animals on the craft, and this is administered to the crew. The Commander, Steven and the others who have been infected are soon on the road to recovery. Their work done, the trio observe the end of Earth on the long-range scanner before the Doctor leads them back to the TARDIS. The TARDIS rematerialises back on the Ark, but 700 years later. They learn that after a second wave of the cold virus introduced a genetic weakness into the humans the Monoids staged a coup and took control. They have completed the statue in the image of themselves, and now have voice communicators and use numerical emblems to distinguish each other. The surviving humans are now the Monoids' slaves, and the Doctor and his friends are sent to the kitchen to help to prepare meals for the Monoids. Two humans, Venussa and Dassuk, believe that the moment of their liberation is at hand. Steven tries to help them in a revolt, which is unsuccessful. The arrival on Refusis is close at hand and a landing pod is prepared. Monoid 1 wants to make sure that the new world is inhabited only by Monoids, despite promises that the human population will be allowed to live there too. A landing party is assembled—the Doctor, Dodo, Monoid 2 and a subject Guardian named Yendom—and they soon reach Refusis II and start to investigate. A stately castle, which seems to be empty, is in fact occupied by the Refusians, giant beings rendered invisible by solar flares. Having anticipated the arrival of the Ark, they built the castle to accommodate the colonists. They welcome their guests, but want to share the planet only with other peaceful beings. Monoid 2 and Yendom flee the castle, and en route Yendom realises that the humans will not be allowed to reach Refusis with the Monoids. Monoid 2 kills him and shortly afterwards is killed himself when the Refusians destroy the lander. Monoid 1 decides to colonise Refusis without more checks on the planet, but