You're on your own, Ace.
The TARDIS is invaded by an alien presence, and is then destroyed. The Doctor disappears.
Ace, lost and alone, finds herself in a bizarre deserted city ruled by the tyrannical, leech-like monster known as the Process.
Lost voyagers drawn forward from Ancient Gallifrey perform obsessive rituals in the ruins.
The strands of time are tangled in a cat's cradle of dimensions.
Only the Doctor can challenge the rule of the Process and restore the stolen Future.
But the Doctor was destroyed long ago, before Time began.