The Doctor and Romana arrive on the marsh moon of Delta Magna in search of the next segment of the Key to Time. They are caught in the conflict between the native Swampies and the crew of a chemical refinery. The presence of a gun runner complicates matters; to make things worse, the Swampies intend to awaken Kroll, the giant god that lives beneath the swamps.
"James Compton is paid by wealthy Howard Townsend to photograph his mistress Simone . Intimate photo sessions lead to an affair. Simone is kidnapped and he is being blackmailed over the affair by the kidnappers. Some violent scenes."
Durante la Primera Guerra Mundial, un submarino que lleva prisioneros de guerra cambia el rumbo repentinamente, lo que provoca que se pierda en el mar. La nave termina recalando en una desconocida isla en el Antártico, que parece deshabitada. Lo que nadie sospecha es que allí se esconde un mundo perdido, lleno de seres extinguidos en el resto del planeta y que suponen una verdadera amenaza para la supervivencia de los humanos.
