Thrown off the Time Path, Professor Bernice Summerfield is trapped in early 20th Century London, with only one of the pair of time rings she needs to get home. At the other end of time, her ex-husband Jason Kane finds himself stranded on a dead world, where the queen of the Charrl demands his help to save her dying race. But all he wants to do is find Benny, and return to the 26th Century.