Fresh from some leisurely bants asking Isaac Newton how does he like them apples, Doc and Donna hurtle to a fiery stop aboard a mysterious spaceship, where the first thing the TARDIS regenerates is its Hostile Action Displacement System so it can finally put itself back together in peace.



It turns out their landing pad was off a corridor so long that it punctures the very bounds of the universe and penetrates the inter-cosmic space/not-space nothing no-thing voidy kind of realmy-wealm. But clangs on the hull and a puzzling airlock action put them on edge at the edge of creation.



With only a succession of untranslatable words periodically refurbishing the scenery as clues, Doc and Donna must end the hostile action, and in the process come face to face to face to face with their own worst nightmares: slowing down, being called stupid, and, maybe, even a countdown.