Parts: 6
Writer: Malcolm Hulke
Airdates: 12 January 1974 - 16 February 1974
Production Code: WWW

Doctor: third
Companion: Sarah

Creature Feature: Dinosaurs
Special Guests: UNIT (the Brigadier, Benton, Yates)

Story: At the TARDIS' next landing, the Doctor smugly informs Sarah that, of course, he has brought her back to the right time and place: England in the twentieth century, within a few weeks after they left. They set off to find a phone and call the Brigadier...but the phones don't work, the buses aren't running, and looters are rifling through the stores. In short, London is completely deserted.

The few people that the Doctor and Sarah can find seem to be more interested in robbing stores or attacking them than they are in providing answers, so London's evacuation remains a complete mystery to them - until, while exploring an old warehouse, they are attacked by a flying creature bearing a long snout full of very sharp teeth.

They soon come to realize that London's evacuation is due to the sudden appearance of roving dinosaurs throughout the center of town. Because they appear out of thin air and vanish just as mysteriously, no-one seems to be able to find out where the creatures are coming from or how to prevent it. The Doctor suspects that someone is conducting experiments with time...but what he does not suspect is a secret organization, dedicated to returning the Earth to a more peaceful time before nuclear war and pollution. And they intend to do it by erasing the timelines of everyone on the planet...