The Doctor and Sarah return in the TARDIS to present-day London but are mystified when they find the city completely deserted.

The Doctor plans to capture a dinosaur so that he can discover who is transporting them through time. But Mike Yates is in league with the enemy and is ordered to stop the Doctor.

The Doctor has captured a Tyrannosaurus Rex but the conspirators don't intend for it to remain captive for long. Sarah follows a lead but places herself in the hands of the enemy.

Sarah awakens to discover that she is on a spaceship that left Earth months ago and is heading for a new world. The Doctor is framed for causing the return of the dinosaurs.

Sarah discovers that the spaceship passengers are all victims of a deception, but not all are willing to believe her story.

Dinosaurs are appearing all over London in a last effort to frighten people away as Professor Whitaker prepares to initiate 'Operation Golden Age'.