Beneath the waters on an unnamed planet, Jeff Stone and his party of aquanauts find a thousand-year-old Dalesub in their underwater sea laboratory. Using their water extractor, they are able to pump the water out of the downed sub, thus facilitating repairs. Soon, they have the Dalesub working again, and are almost immediately engaged in a battle against an approaching Dalek patrol. The Dalesub easily dispatches the Daleks, and its human crew celebrates.