Alien Avatar ( TV story ) Alien Avatar was the twelfth episode of series 1 of " K9 " . Synopsis . The Thames is badly polluted by an alien chemical . K9 discovers that telepathic aliens , the Mede s , are imprisoned by Drake , who is trying to duplicate a missing special key to operate their organic starship . K9 rescues the Medes . June discovers Drake ' s plot and helps release their starship . Plot . As they make their way to the River Thames , Starkey explains fishing to K9 . Two CCPC s ask them what they are doing and K9 explains fishing to them . Starkey and K9 arrive to find dead fish . K9 warns him not touch them , as he has detected an unknown alien substance . Starkey picks one up with his fishing net so he can bring it back to the Manor to analyse and accidentally bumps K9 with the fish . This causes a corrosive spot to start on K9 . At Gryffen Manor , Jorjie sings along to music and accidentally elbows Darius , who is carrying a pile of books . Gryffen asks him if he was going to sell the books . Darius denies it , but Gryffen tells him to take them back to the library . Jorjie starts singing again and Gryffen has to raise his voice to get her attention to tell her to keep it down . As Darius goes to the library , he sees two aliens appear and vanish . At Gryffen house , Starkey takes readings of the toxin in the dead fish . It is extraterrestrial . Starkey finds a match : the toxin is chenium , a corrosive byproduct of the manufacture of Qualon 37 , used in the making of inter - dimensional starship s . K9 estimates that if it builds up in the food chain , 85 % of life in the Thames Valley will die . In June ' s office , Drake orders a CCPC to be more persuasive . June tells him she sent her squad to investigate possible alien activity , but they were turned back by Drake ' s unit . Drake is contacted by the CCPC , who tells him the aliens won ' t stop talking . Drake tells June he won ' t " upset " her squad again . He has business to attend to . She leaves . K9 and the team find where the toxin is entering the river . Starkey sees the aliens . They knock him to the ground and disappear . Back at Gryffen ' s house , K9 looks up the aliens in his file . They are the Mede s , a species who can project their images as avatars if they cannot physically be present . The team decide to go to the pollution ' s source . K9 goes through the drains as Darius and Jorjie track him through the streets and Gryffen and Starkey monitor them . K9 ' s transmission starts to break up . In Drake ' s office , June finds the missing schematics for a Fallen Angel on his computer . When Drake arrives , she asks him about his interest in the ship . Before he leaves , she warns that he better not be in possession of the ship . June goes to Gryffen ' s house , where she shows him a blueprint of the Mede starship and the molecular refractor on the top , telling him Drake , not the Department , is exploiting it . The molecular refractor allows the ship to dematerialise and with this he could spy anywhere and not be seen . The gang spots a factory . Gryffen and June analyse an image of the Mede avatar which cannot be seen in infrared . Starkey insists that Gryffen tell June the situation . Gryffen informs her that Darius , Jorjie and K9 are looking for the source of the pollution in North West 12 . June contacts Jorjie and warns her to get out , but she and Darius are caught by CCPCs . Darius and Jorjie are tied up in the factory , where Drake ' s men are experimenting with the refractor . K9 sees the Medes ' avatars , who tell him to come with them . He replies in their language . They take him to the factory , the source of the pollution , where he sees the workers casting chenium . He finds Darius and Jorjie and frees them . Darius and Jorjie are recaptured . June arrives , takes control of the CCPCs , and the CCPCs take the workers away . K9 asks Starkey to help him deliver the molecular refractor to the Medes and tells June that Drake had the Medes locked up . K9 , Starkey and June gives the Medes the refractor , apologise for what Drake did to them and let them go . The Medes clean up the pollution and repair the damage to K9 before they leave in their ship . After noting the " awesome " day they had , Starkey asks K9 if he wants to go fishing . K9 cheerfully refuses . References . " to be added " Story notes . Ratings . " to be added " Myths . " to be added " Filming locations . " to be added " Continuity . " to be added " Home video releases . This episode is featured in the following DVD sets :