The Doctor and Antimony arrive on the planet Santiny, just as it comes under attack by General Tannis and his Canisian battle fleet. Meanwhile, his other companion, Ace, finds herself under the guidance of the mysterious Casmus, who seems to foresee an important and unusual role in store for her. As the adventure lurches from Santiny to contemporary London and on to Gallifrey, it becomes clear that the Canisians' next target is to be Earth.

First webcast on BBCi and also starring Sophie Aldred, Anthony Stewart Head, and Leonard Fenton, this original audio adventure unites elements of the Doctor's past with bold and original ideas for his future.