Separated from his companions, the Doctor attempts to find solace in the history of his favourite planet – Earth – but instead discovers new threats lying in wait. Travelling from twentieth-century East Berlin to sixteenth-century Strasbourg, the Doctor encounters creatures from other realities: monsters beneath the waves, and human beings determined to exploit their fellow man. But how long can he survive without a friend? On the waves of the Indian Ocean, all the prisoners aboard the Lady Juliana have fallen into a trance... except a single girl. Mary Wade desperately needs a doctor - and only one will help her.