Mud, barbed wire, the smell of death… The year is 1917 and the TARDIS had materialised on the Western Front during the First World War. Or had it? For very soon the Doctor found himself pursued by the soldiers of Ancient Rome; and then he and his companions were reliving the American Civil War of 1863. And was this really Earth, or just a mock-up created by the War Lords? As Doctor Who solves the mystery, he has to admit he is faced with an evil of such magnitude that he cannot combat it on his own - he has to call for the help of his own people, the Time Lords.