Enlightenment ( TV story ) Enlightenment was the fifth story in season 20 of " Doctor Who " . It saw the introduction of the Eternal s . It also saw the conclusion of the Black Guardian trilogy , with the redemption of Turlough and the first appearance of the White Guardian since " The Ribos Operation " . A large number of model shots were used in this story to create the racing scenes and their associated locations . Synopsis . An Edwardian yacht in deep space races around the planets . There is a double agent in the TARDIS crew . The White Guardian warns the Fifth Doctor of great danger . Turlough must finally choose sides and at the end of the race lies the prize of Enlightenment . Plot . Part one . Turlough ' s sabotage of the TARDIS has left the control room dark and on back - up lights until the systems are repaired . Tegan and Turlough play chess . The Doctor thinks he hears a voice calling him . He instructs Turlough and Tegan to increase the power as he walks into the corridor . He sees the White Guardian having trouble materialising in the TARDIS . Trying to make out what the Guardian is saying , the Doctor learns danger awaits him . He is given a set of co - ordinates . Before the White Guardian can explain further , the Black Guardian appears and interrupts the communication . The Doctor sets the co - ordinates and the TARDIS materialises in what appears to be a ship ' s hold . Leaving Tegan in the TARDIS in case the White Guardian tries to contact them again , he and Turlough leave to explore , barely avoiding one of the officers . The officer has a mechanical , blank expression and is dressed in an Edwardian naval uniform . The Doctor and Turlough enter a room and find it occupied by the crew of the ship . After being ignored and then confronted by the crew , who think the Doctor is their new cook , the Doctor speaks with the crew and learns that they remember nothing of coming aboard . They have been below decks the whole time and the ship has been entered in some sort of race . Tegan leaves the TARDIS and meets the ship ' s first mate , Marriner . An officer with the same distant look escorts the Doctor and Turlough to see Captain Striker , who offers them dinner . The dinner is interrupted when the wind picks up and the officers announce that the race has begun . In the wheelhouse , the Doctor sees a map of the race course , complete with " marker buoys " which he recognises as the planet s of Earth ' s sol ar system . Marriner operates anachronistic electronic controls ; a viewscreen activates to show the other contestants - a Greek trireme , a 17th century pirate ship and other vessels from other times , all floating in deep space . Part two . Striker and his officers are Eternal s , beings who live in the " trackless wastes of eternity , " as opposed to the Doctor and his companions , who are " Ephemeral s . " As the ships round Venus , the trireme captained by Critas the Greek explodes when it tries to overtake the pirate ship . Striker believes it was the gravitational pull that did it , but the Doctor suspects otherwise . Tegan feels ill , so Marriner escorts her to a room which she soon realises is a mixture of her room in the TARDIS and her rooms in Brisbane - they have been reading her mind . Marriner seems quite taken by Tegan , finding her mind fascinating and full of life . In conversation with Striker , the Doctor learns that Eternals use Ephemerals for their thoughts and ideas . The Eternals have lived for so long they are unable to think for themselves . They need human minds to give them existence and entertainment — that is why the ships use human crews . The purpose of the race , however , is more than entertainment . The prize is Enlightenment , the wisdom to know everything . The TARDIS is found by the Eternals , who make it vanish . Trapped on board the Edwardian ship , the Doctor and his companions go on deck in space suits . Turlough hears the voice of the Black Guardian taunting him , saying that he is doomed to eternal life aboard the ship . Unable to take the strain , he leaps overboard into space . Part three . Turlough is rescued by the " Buccaneer " , the pirate ship commanded by Captain Wrack . She toys sadistically with Turlough with a knife , but he convinces her that he jumped overboard to throw in his lot with her , to find out the secret of how she will win the race . Wrack sends her first mate to present Captain Davey , one of the other competitors , with a jewelled sword , and party invitations to the other captains . On board the Edwardian ship , Striker refuses the invitation , but the Doctor accepts , hoping to retrieve Turlough . Marriner offers to escort Tegan and the Doctor to the " Buccaneer " as an asteroid storm hits the ships . As Davey ' s ship draws level with the " Buccaneer " , Wrack takes Turlough down in the hold and shows him the entrance to a locked chamber with a vacuum shield , but leaves him outside when she enters . Through the door , Turlough hears the voice of the Black Guardian . Davey ' s ship explodes , apparently hit by an asteroid . The Doctor , though , again suspects otherwise , especially since , like Critas ' s ship , Davey was also challenging the " Buccaneer " . On board the " Buccaneer " for the party , the Doctor and Tegan mingle . Turlough sneaks off to examine the locked chamber . He finds an eye - shaped grid open to space , but a pirate locks the door and turns off the vacuum shield . Fortunately , the Doctor finds Turlough before he suffocates . The Doctor notices the eye - shaped projector above the grid . He theorises that this must be how Wrack transmits the power to destroy the other ships , with some sort of focus . He remembers Critas was wearing an out - of - period clasp with a red crystal . Turlough tells him of Wrack ' s gift to Davey and the Doctor realises the red crystal is the focus . Before they can act on it , they are captured by Wrack ' s first mate . Meanwhile , Wrack has managed to lure Tegan away from the party to her wheelhouse . She freezes her in time and plants a red crystal in her tiara . Part four . Brought before Wrack , Turlough accuses the Doctor of being a spy and claims he was trying to capture him . Wrack sends the Doctor , Tegan and Marriner back to the Edwardian ship . The Doctor believes Turlough is trying to prove himself trustworthy by stopping Wrack . Unfortunately , Wrack sees into Turlough ' s mind . She is about to sentence him to walk to plank . She pauses when Turlough tells her that he , too , serves the Black Guardian . As the ships near the crystalline space station of the Enlighteners , the " Buccaneer " pulls level with the Edwardian ship . Wrack brings Turlough again to the chamber , this time letting him witness her summoning the power of the Black Guardian . The Doctor , seeing the " Buccaneer " pull close , realises the focus must have been smuggled aboard somehow . When he describes it , Tegan tells him about the crystal in the tiara . The Doctor smashes the crystal , but only multiplies the power by the number of fragments . The Doctor gathers the pieces , rushes up to the deck and , just in time , hurls them overboard . They explode . The wind dies and Wrack pulls ahead of the Edwardian ship . The Doctor demands the TARDIS be released to him to stop Wrack from winning and Striker reveals that it was concealed in the Doctor ' s own mind . Travelling in it to the " Buccaneer " , the Doctor tries to reason with Wrack , but her first mate shows up with Turlough and she orders the Doctor thrown into space . While Tegan watches from the Edwardian ship , two bodies are ejected into space and the " Buccaneer " reaches the finish . Marriner is fascinated by the grief that Tegan experiences while believing the Doctor was killed by Wrack . The human crew of the " Buccaneer " vanish as Tegan , Striker and Marriner board to give their respects to the victor . The Enlighteners turn out to be the Black and White Guardians and the winner is the Doctor , who brought the ship in with Turlough ' s help when Wrack and her first mate met with an " accident . " The Doctor , however , refuses the diamond crystal holding Enlightenment , saying that he ' s not ready for it . The White Guardian dismisses Striker and Marriner . Marriner resists ; he wants to stay with Tegan . However , neither Tegan nor the White Guardian is moved by his pleading . He and Striker vanish into eternity . As Turlough helped the Doctor bring the ship in , he is entitled to a portion of the prize . The Black Guardian reminds Turlough of their bargain and says that he can give up the diamond or sacrifice the Doctor to gain both Enlightenment and the TARDIS . Turlough struggles with the decision . He hurls the diamond at the Black Guardian , who vanishes in screams and flames . The Doctor points out that Enlightenment was not the diamond , but the choice itself . The White Guardian warns again that the Black Guardian will return , even angrier now that he has been thwarted twice . He vanishes . Turlough asks the Doctor to take him back to his home planet , and the Doctor agrees . Home video and audio releases . DVD releases . This story was released as a two disc set as part of the DVD set " The Black Guardian Trilogy " . The second DVD was a Special Edition movie - length feature with added modern CGI , a 5 . 1 remix and 16 : 9 widescreen . Contents :