On the planet Mondaran, Willoway leads the resistance fighters against the Cybermen, conquerors of the planet. Reinforcements are called from Telos, including Junior Cyber-Leader Kroton. Following his capture and interrogation, Willoway dies. Kroton is 'puzzled' by his sacrifice and tracks down fellow rebels, Marilka and her lover Pendar. When the rebels are betrayed by the businessman Zarek, Kroton helps Pendar escape and takes him away from the city. Suspecting Kroton's erratic behaviour, the Cyber-Leader tracks them down. Turning against the Cybermen, Kroton helps the rebels escape to the safety of the Forest of Lorn, then removes the craft and takes it into space. Without fuel, batteries drained and unable to return, Kroton drifts on.