The Gift ( TV story ) The Gift was the sixth and final story in the third series of " The Sarah Jane Adventures " . It was notable for containing the only televised direct reference to a family of Raxacoricofallapatorian s other than the Slitheen , namely their rivals , the Blathereen . It also established that Raxicoricofallapatorians are not exclusively green - skinned . Rather , some individuals of this story had red - brown - toned skin . Though long a concept explored in prose representations of the RTD creations , other families had never been named , leaving casual viewers of " SJA " and " Doctor Who " to think that " Slitheen " was the name of a species . The story also had one of the most extensive uses of K9 in " SJA " history , in which he unusually , though not unprecedentedly , left 13 Bannerman Road for much of the story . Synopsis . When the Slitheen ' s latest scheme to destroy Earth for profit is foiled , another family from the Slitheen ' s planet arrive , the Blathereen . Though they seem helpful , can they be trusted ? As a generous gesture of peace , the Blathereen gift the gang with a plant called Rakweed , which could end world hunger . However , the Rakweed goes wild , spreading spores about London and infecting people , including Luke . Sarah must fight alone , not only to save the Earth , but also her son . Meanwhile , Clyde smuggles K9 into school to help him cheat at a test , and he , Rani and the metal dog find themselves trapped in the school — surronded by Rakweed . Can the team work together across Ealing — and Antarctica — to prevent Rakweed from devouring the entire planet ? Plot . Part one . Sarah and the gang chase a child Slitheen into a warehouse , where a disguised Slitheen sets up the countdown for a matter compressor that will form a web around the Earth ' s orbit to squash its huge reserves of carbon , transforming it into a very large diamond . However , two orange - skinned Blathereen arrive and teleport the Slitheen onto their ship . They state that they hunt Slitheen without profit . They introduce themselves as Tree and Leef Blathereen , and invite themselves to tea at Rani ' s house . Whilst there , the Blathereen reveal that Raxacoricofallapatorius was once the most admired planet in the Raxas Alliance , governed by the Blathereen , until the Slitheen came into power . Their economy was destroyed , and eventually the Raxacoricofallapatorians revolted against the Slitheen ; some were brought to justice , but some escaped to distant planets to gain money . The Blathereen returned to power and started to capture the various Slitheen . The Blathereen give Earth a gift : a pot of Rakweed . They say it can survive in even the harshest conditions , and would end Earth ' s famine . With Sarah as their ambassador , the Blathereen could form an alliance with Earth . Clyde is suspicious . After the Blathereen leave , Mr Smith analyses the plant and concludes that it is , as far as he can tell , harmless . With the alien stuff dealt with , Sarah orders the kids to bed since they have a biology test tomorrow . Clyde , having completely forgotten about it , is horrified and decides to take drastic action . After subtly getting K9 to reveal his knowledge of GCSE Biology , Clyde picks him up and absconds with him , intending to use him to cheat ; Mr . Smith feigns ignorance since he welcomes a break from ' the dog ' . Whilst getting dressed , Luke can ' t find his tie and goes into the attic to look for it . The Rakweed has mutated and released harmful spores into the atmosphere . Luke accidentally inhales some spores and becomes properly ill for the first time , since the Bane gave him perfect health . Sarah decides that Luke has to stay home , and Rani is concerned . In school , Rani learns that Clyde has K9 to help him , and will talk to him through an earpiece , to her mingled fury at the idea of cheating and fear if K9 is discovered . Sarah discovers the Rakweed , and Mr Smith explains that the plant has mutated and is releasing spores across the Earth that will infect humans who may pose a threat to the Blathereen , and more Rakweed has grown outside Sarah ' s house on Bannerman Road . A news report reveals that the Rakweed spores are already having an effect , with people collapsing from strange red and black marks on their skin . What ' s more , at the current rate of propagation , the plant will have seeded the whole of London within hours , and within a week the entire Earth will be infected . Mr Smith also reveals that the Rakweed will put humans into a coma from which they will never awaken . Sarah sees red and black spots on Luke ' s chest and the Rakweed releases a massive wave of spores that head towards Sarah and Luke . Sarah shouts for Mr Smith to somehow stop them as the Rakweed spores come closer . Part two . Mr Smith activates at the last moment and , using the cooling mechanism built into his system , diverts the spores towards the fans and away from Sarah and Luke . However , doing this has depleted his energy . To prevent it from creating more spores , Sarah throws the Rakweed into her safe . Mr Smith explains that the Blathereen use the Rakweed as a weapon to destroy anyone who stands in their path , and while Luke is a lot stronger than other humans , being able to resist the effects for longer , he inhaled the spores directly into his lungs . He can stand the spores for longer but not forever . Meanwhile , Clyde and Rani prepare to begin their exam . Clyde slides the question papers under the table for K9 to analyse and asks for the answers to be relayed to him via the metal earpiece . K9 initially refuses , stating that his order is unethical , but is soon persuaded by Clyde , who says to K9 , " You said a test was one human demonstrating intellectual superiority over others . I brought a supercomputer into school , that ' s pretty smart , wouldn ' t you say ? " K9 considers by flashing his eye light . He finally agrees and Clyde says he wants the answers " short and to the point " . In the attic , Mr Smith analyses Luke and determines that they have half an hour before he is completely poisoned , being at 63 % , and that he is unable to find an antidote as the spores are constantly adapting ; it could take him days to create one himself , and even then it might not work . Clyde is caught cheating when K9 is discovered by the teacher , but everyone is distracted when the Rakweed plants spawn in the classroom , infecting the teacher and creating panic among the students . Sarah asks Mr Smith to locate the Blathereen using the teleportation co - ordinates she recorded , and learns that they are hiding in Antarctica . In their base , the Blathereen mock Sarah ' s greed for glory over accepting the Rakweed and gloat over their plan ' s success . Mr Smith teleports Sarah to the Blathereen base , despite the fact that he only has enough energy for a one - way trip , but Sarah is not in a joking mood and determined to save her son at any cost . The Blathereen , still gloating and gorging aboard their ship , are flabbergasted when Sarah teleports into their midst , packing a six - barreled super - soaker loaded with vinegar and threatening to blast them into oblivion if they so much as move without her consent . Rani learns about the Rakweed ' s effects after finding some of the students unconscious , and calls Luke , who is now 87 % infected and falls unconscious mid - conversation . Sarah bargains with the Blathereen to destroy the Rakweed , but she is tricked and strapped into a chair which , they say , " cost a fortune ! ! " Clyde , Rani and K9 discover that the Rakweed has spread throughout the school grounds and find themselves trapped in the building . Meanwhile , Sarah discovers that the Blathereen are addicted to eating Rakweed , and plan to cover the Earth with it , as it has a high value on the galactic market . They soon reveal their true identities — members of a family , descended from both the Slitheen and the Blathereen , known as the Slitheen - Blathereen family , who tend to take after the greedy Slitheen more than the noble Blathereen . Clyde and Rani discover from news reports that the spores are spreading across the whole of London , with the districts of Southall , Perivale , Acton and Chiswick all reporting serious cases . They are nearly infected but then the school bell rings , neutralising the Rakweed spores and some actual Rakweed . Sarah learns that the Rakweed plants somehow rely heavily on communication with each other in order to spread . She breaks out of her restraints and manipulates their teleportation device to return home , only to discover Luke unconscious . K9 utilises the school bells to defeat the Rakweed within the building . Clyde uses K9 to connect with Mr Smith to send the frequency level required to spread the noise across London ( 1421 . 09 Hertz ) . Mr Smith hacks into every single device that could emit those levels of noise and are within the affected areas , warning Sarah and the kids to brace themselves since it will be very loud . True to his word , everything from microwaves , car alarms and mobile phones go off in a great cacophony of noise , destroying the Rakweed . Luke and the other infected people recover from the deadly spores , and he and Sarah embrace . Furious at the upsetting of their plans , the Slitheen - Blathereen teleport into the attic and confront Sarah and the gang . Sarah gives them a final chance to simply call it off and leave , but they insist on committing murder most foul which leaves her with no choice . On Sarah ' s request , Mr Smith activates the alarm , which initially confuses them since their smell is highly sensitive but soon causes the Slitheen - Blathereen ' s stomachs to swell , then explode , covering everyone and everything in their gory remains . K9 deems the " disintegration successful " ( " You " don ' t " say ! " , is Mr Smith ' s response ) and explains that the undigested Rakweed in their stomachs reacted to the alarm , creating an uncontainable amount of methane gas and causing them to " fart themselves to death . " As punishment for trying to cheat , Clyde is told to clean up the mess , while the others prepare a barbecue . Later , Clyde walks out , mop in hand and still covered in goop , while the rest of the group has changed into casual , clean clothes , telling Sarah he has finished cleaning . He discovers she overcooked the sausage and tells her , " You cremated our picnic ! " After switching to a fresh outfit and washing up , Clyde joins his friends at the outdoor picnic table for a leisurely meal . During the epilogue , Sarah comments on the possibility that one day some alien races will want to " help " humanity , the importance of friendship and that " Earth could become a shining example to the entire universe " . Story notes . Filming locations . " to be added "