Inside the TARDIS, the Fourth Doctor, Romana, Adric, and K9, while travelling between E-Space and the normal universe (N-Space), become trapped in a white null space between the universes. Elsewhere in the void, a slave vessel, run by Captain Rorvik, has also become trapped. It uses members of the leonine Tharil race as their navigators. On becoming stuck, the current navigator, Biroc, escapes the ship and makes his way to the TARDIS on the winds of time. Biroc warns the TARDIS crew of Rorvik's treachery before disappearing. K9's memory wafers are shredded by the winds of time, leaving him functional but lacking long-term memories. The Doctor leaves on his own to explore the null space. He encounters some robots, called Gundans.