After Martha says goodbye to the Doctor and leaves, he is surprised to find a problem with the TARDIS. Suddenly, a man materializes - the Fifth Doctor. But why's he here, and what's happened to the TARDIS?

Who is attacking a speeding bullet train on the edges of a distant galaxy? Why are seismologists going missing from 21st century Earth? Who is defacing some of history’s most iconic paintings? Why is a Dalek trying to make contact with the Doctor? And just what hold does the mesmeric Rasputin have over Tsar Nicholas in 1916 Russia? In her last adventure, The Thirteenth Doctor must fight for her very existence, against her deadliest enemies: the Daleks, the Cybermen and her arch-nemesis, the Master.