The TARDIS is drawn into an empty white void, somewhere between universes. But they are not the only ones trapped there.
When Rorvik learns that Romana is a time sensitive, he takes her prisoner, forcing her to find a way out of the void. The Doctor attempts to discover what lies beyond the mirror.
As the void begins to shrink around them, Rorvik plans to take desperate measures to escape through the mirror. The Doctor discovers the dark secret of the Tharils' past.
With the void collapsing around them, time is running out. Rorvik ignores the Doctor's warnings and takes a desperate gamble which could have fatal consequences.