On the way to Gallifrey to return Romana to the High Council of Time Lords, the TARDIS and its occupants end up in another universe called E-Space, because they have passed through a charged vacuum emboitment. They land on the planet Alzarius, near a small civilization of humanoids who came from Terradon in a ship they call the Starliner. The oligarchy in charge—three senior colonists called The Deciders—has been trying to repair the spacecraft for generations. One of the bright young colonists is Adric (Matthew Waterhouse) who has a badge of mathematical excellence, but his brother Varsh (Richard Willis) is a member of the Outlers, who reject the regimented society of the Deciders and steal food to survive.
Strange eggs have begun to appear in riverfruit, which First Decider Draith (Leonard Maguire) interprets as an omen of Mistfall, which threatens the natural balance of the world. The colonists move into the Starliner to protect themselves. Adric tries to steal riverfruit for his brother. Draith pursues him, falls into the river, and is pulled under by a strange force. His last words are “Tell Dexeter we’ve come full circle.” Adric flees into the forest and the Doctor and Romana take him into the TARDIS to treat his leg-wound, which heals with remarkable rapidity. The Doctor leaves to investigate the planet, and Adric invites Varsh and the Outlers into the TARDIS to protect them from Mistfall.
The other Deciders, Garif (Alan Rowe) and Nefred (James Bree), have ordered the Starliner doors closed. Draith and Keara (June Page), the Outler daughter of prominent citizen Login (George Baker), are still outside. Login is appointed Third Decider when it is learned that Draith has died. Marshmen, an aggressive humanoid species bearing a remarkable resemblance to the Creature from the Black Lagoon, appear in droves and Marshspiders hatch from the eggs in the riverfruit. The Marshmen beat on the walls of the Starliner to no avail, but the Doctor uses his sonic screwdriver to get in, followed by a young and inquisitive Marshchild (Norman Bacon). The Doctor is appalled when chief scientist Dexeter (Tony Callin) starts to experiment on the Marshchild.
Marshmen have carried the TARDIS into a cave (much as the Morlocks did to the Time Machine), hoping to use it as a battering ram against the Starliner. Romana is bitten by a Marshspider and seems possessed, and the Marshmen knock K9’s head off. Adric panics and figures out how to materialize the TARDIS inside the Starliner. When the Outlers emerge, the Doctor brings the TARDIS back to the cave, where he finds Romana alert but amnesiac. The Doctor scoops up the remains of the Marshspider and brings the TARDIS back into the Starliner, defending himself from the Marshmen by brandishing K9’s head. Dexeter has cruelly provoked the Marshchild to kill him. The Doctor denounces the Deciders, revealing secret ship controls that show the Starliner has been able to take off for centuries, but no-one knows how to fly it.
The Doctor examines the Marshspider and the Marshchild and finds they are from the same DNA source. Romana opens the emergency exits and allows the Marshmen to enter the ship. Nefred is mortally wounded, and his last words are, “The colonists cannot return to the planet Terradon because they have never been there.” As the Doctor learns, the Alzarins are a subspecies of Marshmen, who wiped out the original Terradon colonists and then evolved to take their place. The Doctor cures Romana and determines that for 40,000 generations spiders, Marshmen, and humanoids have all been part of the same species, come full circle. Oxygen is used to force out the Marshmen, back to the swamps. Adric’s brother Varsh has been killed, and Adric stows away in the TARDIS.
Alzarius occupies in E-space precisely the same co-ordinates as Gallifrey in our space (1001100 zero by 02 from galactic zero center). E-space is short for Exo-space-time-continuum. The name Adric is an anagram of Dirac; Paul Adrien Maurice Dirac was the first to predict the existence of antimatter in 1930, and like Adric he received a badge of mathematical excellence in the form of the 1933 Nobel Prize in Physics, along with Erwin Schrodinger. Full Circle is the first volume of the E-space Trilogy, the others being State of Decay and Warrior’s Gate. The story received rave reviews, and I think it deserved them. It was the first Doctor Who story to be written by a fan, Andrew Smith. The script was universally praised, as was the acting. Even the Marshmen were praised, though they were clearly wearing zippered suits. Nobody much bothered with the dicey genetics.