With the secrets of time-travel restored to him after his long exile on Earth, the Doctor decides to test out the TARDIS with a trip into the past. Accompanying him are his assistant, Jo, and an old friend, scientist Liz Shaw. Soon after landing, the travellers realise they have landed at one of the most significant periods of Earth's history — and one of the most dangerous... It is Russia, 1916, and Europe is in the grip of the Great War. With the TARDIS confiscated by Imperial guards, its crew find themselves trapped in a country on the brink of revolution.