The Doctor decides to modify some of the TARDIS's systems, so disables most of the major ships systems. During this process, they encounter a stranded ship from Skonnos. They the assist the remaining crew member who then kidnaps Romana and leaves the Doctor stranded in the TARDIS.

As they travel deeper into the Nimon power complex, the Doctor and Romana start to suspect that there is a lot more to the Nimon than meets the eye and that they may be seeing the start of a invasion of the planet Skonnos.