The destruction of the causal nexus continues, a new reality has been created, Anne Travers is sent into her past to retrieve a man who bears a shocking resemblance to Brigadier Alistair Lethbridge-Stewart. February 1969, and school teacher Archie Lethbridge-Stewart lives an ordinary life. His old pupil, Owain Vine, is having strange visions. On the news it seems London is being evacuated - a major gas leak and bears breaking free of London zoo. Can these events be connected? Linking all this is a strange old man who insists he knows Archie. Who is this mysterious figure? What does he know about the future? And why should Archie and Owain risk everything to go with the old man to London? A brand new adventure featuring Brigadier Lethbridge-Stewart in the classic era of Doctor Who. Based on the characters created by Mervyn Haisman and Henry Lincoln.