Someone is interfering with time. To find the culprit, the Doctor, Rose and Captain Jack arrive on modern Earth and... discover a Neanderthal whose race went extinct 28 thousand years ago. Only a journey to the primeval dawn of humanity will help solve the mystery. Who are these mysterious people from the distant future, now living in the distant past? What kind of scary monsters are trying to escape from behind the Gray Door? Will Rose marry the caveman? Caught between three very different representatives of humanity - past, present and future - the Doctor, Rose and Captain Jack must discover the truth about Osterberg's experiment before the monstrous Hi-Brectors break free and change the course of history forever... Featuring Doctor Rose and Captain Jack Harkness, played by Christopher Ecclestone, Billie Piper and John Barrowman in the Doctor Who series.