they died out years ago. He gives the Doctor 24 hours to discover the cause of the virus, or else he and his companions must leave. While Hobson deals with the Gravitron, which is becoming difficult to control with fewer staff, the Doctor focuses on the cause of the viral disease. In the sickbay, Polly and Jamie are attacked by a Cyberman, which stuns them with electricity from his hand and leaves with another patient's body. The Gravitron isn't working because some antennae on the Moon's surface are broken. Jules and Franz go out to fix them but are ambushed by two Cybermen and beaten to death. The Doctor can't work out the cause of the disease and is ordered to leave by Hobson. Polly makes some coffee and another crew member gets infected. The Doctor works out that the neurotropic virus has been spread through infected sugar from the food stores and is an organised scheme to destabilise the crew. A Cyberman who had been posing as a patient in bed reveals himself and aims his gun at them. Another Cyberman emerges and kills Bob when he tries to attack the other with a metal bar. The Cybermen recognise the Doctor and use their weapons to take control of the central control centre of the Moonbase while confining Polly and Ben to the sickbay. The Cybermen reveal that they want to use the Gravitron to destroy all life on Earth by altering the weather. On board the cyber-ship Evans, Jules and Ralph are conditioned to obey the Cybermen like zombie slaves. They are taken to the base and are sent into the heart of the Gravitron to subvert it. The Cybermen have been entering and leaving the base using a tunnel that goes into the food stores, explaining the drops in air pressure. Using fire extinguishers, nail varnish remover and other objects that dissolve plastic, Ben, Polly and a recovered Jamie lead a fightback from their incarceration in the medical wing. The three Cybermen in the initial attack force are destroyed. Benoit goes outside to see what happened to Jules and Franz. He only finds their spacesuits, and is chased by a Cyberman. Ben puts some of the solvent in a bottle and goes out. He then throws the bottle at the Cyberman's chest unit, killing it and saving Benoit. The crew block off the hole in the food