Full Circle ( TV story ) Full Circle was the third story of Season 18 of " Doctor Who " and the first story of the E - Space trilogy . It introduced Matthew Waterhouse as companion Adric . Synopsis . The TARDIS falls through a CVE into E - Space and arrives on the planet Alzarius . There the inhabitants of a crashed starliner and a group of young rebels called the Outlers , led by a boy named Varsh and including his brother Adric , are terrorised by a race of Marshmen who emerge from the marshes at a time known as Mistfall . The Doctor discovers that the starliner ' s inhabitants are not the descendants of its original crew , as claimed by their leaders , the Deciders , but evolved Marshmen . With the Time Lord ' s help and encouragement , the starliner is repaired and able to leave the planet . Plot . Part 1 . The Fourth Doctor has K9 implement the coordinates for Gallifrey into the TARDIS console , having been summoned there at the behest of the Time Lord High Council . Romana disappears back to her room and confesses to the Doctor that she doesn ' t want to be returned to the Time Lords to live out her life on Gallifrey . While the TARDIS is in flight , it passes through a bizarre space / time event and into a green void . While the Doctor attempts to figure out what happened , the TARDIS lands and the scanner shows an image of Gallifrey , but they step outside to find themselves somewhere completely different . Nearby is a small but sustainable civilisation of humanoids who live between a river and a grounded but not irreparable spaceship called the Starliner . They came to the planet Alzarius from Terradon . Much of the focus of society is on repairing their craft . It is an oligarchy ruled by three self - selecting senior colonists knows as Deciders . They ensure the smooth running and order of their adopted world and lay particular store on technical ability . One of the brightest of the younger generation of colonists is Adric , who bears a Badge of Mathematical Excellence in recognition of his computational skills . Adric ' s brother , Varsh , has rejected the regimented society of the Starliner . He leads a band of rebels called Outlers , who steal harvested riverfruit and other foods to survive . The Outlers attempt to steal some of these riverfruits , but fail and retreat to their cave . Not all is well in the colony . Strange eggs have started to appear in the riverfruit . This is interpreted by First Decider Draith and scientists Dexeter arrive to examine the inside of riverfruits . In the TARDIS , the Doctor tries to determine their location , but the scanner and coordinates are both stating that the planet is Gallifrey . Back in to the village , Draith , using the precious System Files of the Starliner , views the appearance of these eggs as an omen of Mistfall , a strange periodic change to the planet during which the natural balance of society is threatened . In the Outlers cave , Adric makes a plea to Varsh to allow him to join the Outlers , but none of the members are convinced of his intentions or loyalty and come up with a means of him proving himself . Soon Mistfall begins , and the colonists move into the Starliner to protect themselves , apparently in a well prepared manner . Adric chooses the moment of confusion to try and steal some riverfruit to prove himself to his brother . Draith gives chase to his young protégé but falls in the river – only to be dragged beneath the waves by a strange force . His last words are aimed at the chief scientists of the colony : “ Tell Dexeter we ' ve come full circle ! " Adric muses on this as he heads into the forest in panic , finding his way into the TARDIS . The Doctor and Romana take him in and tend to his leg wound , which recovers remarkably quickly . The Doctor and Romana conclude that the reason the scanner isn ' t working is down to the negative coordinates , something which their space doesn ' t have , meaning that they are no longer in their space . The Doctor heads off to investigate the marshes that Adric mentioned in his delirium , while Adric attracts Varsh and the other Outlers to the protection of the TARDIS . The two other Deciders , Garif and Nefred , have meanwhile ordered the Starliner doors closed as per procedure , knowing that both Draith and Keara , an Outler and the daughter of a prominent citizen called Login , have not entered the ship safely . Despite his worries , Login soon accepts a position as Third Decider when it is determined that Draith has died . It is as well the doors have been closed . At the swamp , the Doctor and K9 are still examining the mist , when humanoid , aggressive Marshmen begin to appear from underwater , looking threatening . Part 2 . The Marshmen continue to rise from the water as the Doctor observes . In the Outlers cave , Adric is telling the others about the TARDIS and Varsh , now convinced of the danger of Mistfall , decides to relocate there and take control , against Adric ' s wishes . The Doctor and K9 move out of sight as the Marshmen move away and the Doctor has K9 follow them while he returns to the TARDIS . While Romana works , the Outlers , followed by Adric , arrive at the TARDIS and declare their intention to seize it . On the Starliner , Nefred and Gariff summon Login and offer him the position of third decider , which he accepts . K9 continues to follow the Marshmen , until they cross a small river bed he is unable to cross . Romana is still at the mercy of the Outlers before Adric intervenes and Romana regains control . Suddenly , the TARDIS rocks violently , as if it were being carried . The Doctor returns to where the TARDIS was to find it gone without trace . He proceeds further down to hill and stumbles across the Starliner in the distance ; he heads over to it . While the Marshmen beat on the walls of the Starliner to gain entry but the fearsome primitive creatures are not admitted , the Doctor gains entry to the Starliner using his sonic screwdriver , followed by a young and inquisitive Marshchild . Nefred addresses the colony of the Starliner as the Doctor and the Marshchild roam free . The TARDIS stops rocking , but Romana can ' t establish what ' s outside as the scanner still shows pictures of Gallifrey . Romana looks out of the doors to find the TARDIS in the Outler ' s cave , surrounded by Marshmen . The Marshchild , lost and afraid , roams through the Starliner , stumbling across some of the citizens . The Doctor tries to reach out to the Marshchild , but a citzen knocks him unconscious and capture the Marshchild . Both are taken and brought before the Deciders . Gariff orders the Marshchild taken to Dexeter for examination . In the Outlers ' cave , the Marshmen beat on the TARDIS trying to gain entry . Romana decides to venture outside . K9 comes to rescue her and the others from the Marshmen , but he had his head knocked off . Romana and Adric deduce that the Marshmen are intending to use the TARDIS as a battering ram to force their way into the Starliner by throwing it down the mountain . The Deciders continue to question the Doctor , who tells them about Decider Draith and the truth about the mists , making Login hopeful that Keara , his daughter , is still alive . Dexeter then arrives and the Doctor goes with him to examine the Marshchild . Back in the cave , the Marshmen suddenly retreat , and when the group step outside to investigate , Marshspiders start emerging from the riverfruits in the cave . Varsh , Tylos , Keara and Adric retreat into the TARDIS . In a panic , Tylos shuts Romana out ; when Adric tries to open the doors , he accidentally dematerialises the TARDIS without her . Romana is ambushed by the spiders , picking up a riverfruit to fight them off , but a spider bursts out of it . She is bitten by one of the Marshspiders and falls unconscious . Part 3 . The Doctor and Dexeter examine the Marshchild and the Doctor is angered to discover Dexeter has been conducting more experiments on it . Login arrives and arranges a deal with the Doctor that if he helps him find his daughter , he will help locate the TARDIS . Suddenly , the TARDIS arrives . When the Outlers emerge Login is reunited with his daughter , but the Doctor is not impressed not to be reunited with Romana . Thus he pilots the TARDIS back to the cave , and finds an alert but amnesiac Romana . On the Starliner , Varsh , Keara and Tylos are put in front on an enquiry , while Dexeter convinces the Deciders to allow him to experiment on the Marshchild . The Doctor scoops up the remains of a Marshspider and K9 and then reverses his journey once more with Adric and an unconscious Romana in tow . By the time he is back in the Starliner , however , Dexeter has tried to examine the brain of the Marshchild , provoking it to attack , killing both Dexeter and itself in a state of panic . The Doctor sends Adric back to the TARDIS and is so incensed that he turns on the Deciders and denounces their society – revealing secret ship controls that show the Starliner has been ready to pilot from Alzarius for centuries but , for some reason , the farce of constant repair has been continued . The problem it seems is that though the Deciders understand the technical construction of the ship , no one knows how to pilot it . Varsh , Keara and Tylos are put to work doing maintenance on the Starliner systems . The Doctor persuades the Deciders to give him equipment to examine the cells of the Marshspider , Marshchild and Dexeter and also deduces that they are from identical DNA sources . Adric arrives and informs the Doctor that Romana has vanished . When they go back to the TARDIS , they find her room ransacked and go in search of her . At the lower section of the Starliner , Romana , now completely under the influence of the Marshspider ' s venom , releases the emergency exits and allows the Marshmen to invade the Starliner . Part 4 . The Marshmen storm the Starliner in droves and Romana opens another exit allowing more and more of them in . While Varsh , Keara and Tylos are working on the ship , they encounter the invading Marshmen , but Varsh distracts them with the contents of his bag and they flee , but Tylos is killed trying to help someone escape . Varsh and Keara meet up with the Doctor and Adric and the Doctor hustles them into the science unit . The colonists retreat before the creatures , many of whom are more inquisitive than dangerous , but anarchy reigns . The Doctor returns to the TARDIS but is cornered by Romana and the Marshmen . In the science unit , Varsh grows impatient and Adric swaps a microscopes functioning image translator with a broken one . The Doctor tries to break Romana ' s conditioning to no avail , but manages to keep subliminally chained to the TARDIS . In the main book room , the Deciders come up with a plan when the Marshmen begin to invade and the inhabitants evacuate . Nefred is mortally wounded while fleeing , along with many others . In the science unit , the Doctor barricades the door and uses the microscope ( which Adric returns the image translator for ) to examine Dexeter ' s DNA samples . He and the Outlers concoct a serum which should break Romana ' s influence when the Marshmen attack the door and begin breaking in . Login orders the citizens to seal the emergency exits , and then he and Gariff plea with Nefred for guidance , of which he has none other than to ask the Doctor ' s help in piloting the Starliner . His last admission is that the colonists cannot return to Terradon , because they ' ve never been there . Gariff and Login go and search for the Doctor . The Marshmen invade the science unit , but the Doctor manages to keep them at bay using oxygen canisters , as the oxygen contained is too high concentration for them to adapt quickly enough . The possessed Romana enters the unit and attacks the Doctor , before Adric knocks her unconscious with the oxygen in the canister . The Deciders discover the Outlers forcing the Marshmen out . The Doctor uses the protein serum to cure Romana . The Doctor and Romana determine from research that the ship has been maintained for 40 , 000 generations by a species that has three aspects ; spiders , Marshmen , and the current humanoids . The Marshmen continue to attack , and Adric ' s cylinder runs out of oxygen . Varsh remains to fend them off , but as he ' s escaping , he ' s pulled through the closing door and killed , despite Adric ' s attempts to save him . The Doctor has Login flood the Starliner with the oxygen to force the Marshmen ' s retreat , while Adric and Keara mourn Varsh . The Starliner is filled with concentrated oxygen and the Marshmen leave through the emergency exits . The Doctor explains to Gariff and Login that the present - day Alzarians are actually a subspecies of the Marshmen , who wiped out the Starliner ' s original Terradonian crew and then gradually evolved into human form to take their place . They are all from the same DNA and thus have come " full circle " . This is the real secret of the System Files . As the Doctor and the Deciders head to the TARDIS , Adric runs inside and puts the functioning image translator on the console for the Doctor to find . The Doctor shows the Deciders how to operate the ship ' s flight so they can manage on their own , before returning to the TARDIS . In the control room , the Doctor finds an image translator left by Adric , which he uses to ensure where they were . It emerges they have journeyed to this pocket universe through a rare space / time phenomenon known as a Charged Vacuum Emboitment . They then watch the Starliner take off and leave Alzarius . Both the Doctor and Romana forlornly concede that until they find another CVE to escape through , they ' re trapped in E - Space . . . DVD and Video releases . DVD releases . " Full Circle " has been released on DVD in a box set with " State of Decay " and " Warriors Gate " . The box set is titled " The E - Space Trilogy " . Special features include : Editing for the DVD release was completed by the Doctor Who Restoration Team .