The TARDIS arrives at it's next destination, the marsh planet "Delta Magna". Where the Doctor and Romana goes in search of the fifth segment to the Key to Time. Where they discover the native tribal Swampies worships Kroll, a gigantic squid as a god, only to find Kroll has accidentally swallowed the fifth segment and Romana is chosen by the Swampies for sacrifice and The Doctor sets out to save a local refinery from being attacked by Kroll.