Swampies capture Romana and offer her as a sacrifice to a mammoth squid-like god on the third moon of Delta Magna. With Tom Baker.

Doc Holliday is the Doctor's dentist.

Marshal Wyatt Earp seeks Doc Holliday.

Barbara Wright and Ian Chesterton follow one of their pupils to her home address, a junkyard at 76 Totter's Lane where they meet her grandfather, the Doctor. In the Tardis, he takes them all to a Palaeolithic landscape where they encounter a tribe.

Ian and Barbara are aboard the Tardis uninvited! The Doctor ignores Susan's pleas to let them go. The Tardis takes off and travels back to Stone Age times. The crew make the mistake of venturing outside.

The Doctor and leave the TARDIS to explore their new surroundings, but are seen. They are soon captured, thrown in a cave and threatened with death. They only have the secret of fire to bargain with.

The Doctor and his companions use guile and cunning to escape death at the hands of their Stone Age captors. The Doctor decides that the only way to escape is to show the cave dwellers how to make fire.

Doctor must save planet Dulkis, conquered by aliens.