It seems like a regular, routine weekday: Sarah Jane is doing a supermarket shop (and trying not to embarrass Clyde, who is doing his work experience in Betterworth's) while Luke is at the Natural History Museum, helping to catalogue items and set up displays.
But their ordinary day is about to turn extraordinary, as forces from an alien world start to affect Earth and all hell breaks loose. With an icy void opening beneath the chiller cabinet, museum exhibits coming alive and terrifying monsters appearing, Sarah Jane, Luke, Clyde and Rani are soon left fighting for their lives.
Clyde, Rani and Luke have to do a five day work experience in a local business.
Rani Chandra wasn't able to organise a work-experience because her family has just moved to Ealing. She had asked Sarah Jane several times to do the work-experience with her, but Sarah Jane always said no. Rani later tells Sarah Jane that she is doing her work-experience with her father at school, while she tells her parents that she is doing a work experience with Sarah Jane.
Clyde is doing his work experience in Betterworth's when Sarah Jane Smith comes to the supermarket. She is surprised to see that Clyde is working there because she thought he would be working in the head office of a plumbing firm. Sarah Jane and Clyde are talking to each other when Clyde's boss Mr Charlson arrives. He doesn't threat Clyde nicely and makes him responsible for things that Clyde hasn't done, like throwing dog food around. Mr Charlson shouts at Clyde and enjoys it when other people are listening to this. Sarah Jane stops Mr Charlson and asks Clyde in front of him if Clyde could help her. Clyde leaves together with Sarah Jane.
They see Mr Ploughman, a pensioner, who is living close to Sarah Jane. Sarah Jane hasn't seen him since a long time. Mr Ploughman is acting suspiciously and seems to watch someone. Furthermore, Sarah Jane's sonic lipstick is buzzing when Mr Ploughman is around. Then Mr Ploughman runs away. Barriers of food build up after him and barricade Sarah Jane and Clyde's way. Clyde reaches Mr Ploughman at the frozen food section. Clyde struggles with Mr Ploughman and Mr Ploughman is taken away by security guards. Sarah Jane finds Mr Ploughman's black framed glasses and takes them into her pocket.
Meanwhile, Clyde is locked up at the frozen food section. Sarah Jane is afraid that Clyde freezes to death and asks Mr Charlson for help. Mr Charlson however doesn't care and says that Clyde needs saving when he gets hold of him.
Clyde gets out by himself. Mr Charlson shouts at Clyde because, according to Charlson, Clyde was assaulting a pensioner who might sue them. He tells Clyde to clean up everything before the area manager arrives and that Clyde would by lucky if he gets home before midnight. Clyde however doesn't react. He looks at a cube shaped object in his hands.
Then there is a sharp, bright, flash of light and Mr Charlson fells backwards. After this Cornflakes and other ingredients get formed together as cereal monsters, monsters made of chocolate blocks. Clyde walks out of the supermarket without showing any reaction to any of the things that are happening around him. Once Clyde is gone the food just drops onto the floor, the food monsters are gone.
At the museum Sarah Jane sees Mr Ploughman, but worries too much about Luke to think about her old neighbour. She finds out that Luke had stolen Black Diamond of Earnfield and locked himself up in a cupboard. He doesn't want to come out. Sarah Jane realises the diamonds have the same alien markings on it as Clyde's cube shaped object. When Sarah Jane opens the door and comes out of the cupboard, she realises that there is chaos all around. The two security guards are lying unconscious on the floor, Dr Wendeline Minot shouts at Mr Ploughman. Sarah Jane takes out Mr Ploughman's glasses, puts them on. They reveal great swirls of grey mist undulating about Mr Ploughman invisible to everyone but Sarah Jane.
Mr Ploughman looks angrily at Luke and the diamond. Luke touches the diamond and the mummified animals become alive and protect Luke before Ploughman. Luke goes into the next room, a gallery. A swarm of reanimated insects gets together in a humanoid shape and fights against the security staff. Then Luke goes out of the museum. Sarah Jane goes after him but it seems like Luke has vanished.
Meanwhile, Rani Chandra sees Mr Ploughman outside Sarah Jane's house. Rani calls him. Then it seems like Mr Ploughman is waving with his hand but short time later there is a huge rush of air and things are flying around 36 Bannerman Road. Gita Chandra's flowers are jumping outside their vases and form a face. The face is staring at Rani and is threatening her. When Rani runs through the hallway everything drops to the carpet.
Back at Bannerman Road Sarah Jane meets Rani and Gita Chandra. Rani tells Sarah Jane about her experiences with Mr Ploughman. Then they go to Sarah Jane's attic. Mr Smith analyses Mr Ploughman's spectacles. He tells Sarah Jane that they are artefacts from the planet Persopolis. Furthermore he tells Sarah Jane about a Persopolisian control console that crashed on Earth and was divided into three artefacts: the Black Diamond of Earnfield, a Persopolisian base unit and a Persopolisian dice. Any innocent minds who come into close contacts with the reactivated components would be controlled by them used by the devices for self protection. Sarah Jane recognises that these are the two components that Luke and Clyde have taken. Now Rani and Sarah Jane want to find the third component, the Persopolisian base unit.
When Rani puts on the spectacles. She sees a grey trail on the street, from Mr Ploughman. Sarah Jane and Rani get into the car and go after the trail. They realise that Mr Ploughman is going to the Lordwick scrapyard. When they arrive there they see a sign: "Closed today due to family illness." Sarah Jane uses her sonic lipstick to break into the scrapyard.
Then Rani and Sarah Jane find the base unit. Rani takes it and gets controlled by it. Mr Ploughman, Luke and Clyde arrive. Luke and Clyde are still under the control of the artefacts. Mr Ploughman reveals that he is the Persopolisian Janksia who is possessing the body of Mr Ploughman. He crashed on earth a thousands of years ago. In 2009, Mr Ploughman found his space pod and Janksia possessed him. Now he wants to combine the three components of the control consol and fly away with his space ship
Sarah Jane tells Janksia that these components combine into an enormously powerful device, that will destroy southern England if it is used there. Sarah Jane says that she has friends who are able to get Janksia to a safer launch point, like a deserted island or the moon. Janksia just replies that this will delay his journey home. Then he uses his components trying to control Sarah Jane as well. Sarah Jane looses her sonic lipstick, but Luke gets free of Janksia's control and tells Janksia to leave his mum alone. Then Rani and Clyde get free of Janksia's control and Janksia leaves Mr Ploughmans body.
A humanoid figure appears. It is 9 metres high and consists of metal from the scrap yard. Then Luke holds up his diamond and another metal creature begins to form itselfs from the scrap yard parts and attacks the other creature. It looses, but Luke throws the diamond into the garbage compactor. Janksia jumps after the diamond. Clyde tries to save Janksia but isn't able to.
Sarah Jane later finds the Persopolisian dice in the scrapyard where Janksia dropped it when he tried to save it from the crusher.
Then Sarah Jane drives everyone home. Luke and Rani help to put Mr Ploughman into his favourite armchair. When he wakes up Luke tells him that he must have had a nightmare. Mr Ploughman asks Luke to get a few things from the supermarket for him.
Clyde gets a lifetime ban from Betterworth's, but he isn't interested in going shopping there or working there any more.
Sarah Jane asks Mr Smith to create a duplicate of the black diamond which she gives to the Natural History Museum. She also gives them another extraordinary alien jewel, which was a gift to Sarah Jane from a rescued Kisami. In exchange they should make no more fuss about Luke.
- Sarah Jane Smith
- Luke Smith
- Clyde Langer
- Rani Chandra
- Mr Smith
- Gita Chandra
- Dr Wendeline Minot
- Sarah Jane visited the Natural History Museum with her Aunt Lavinia.
- Gita has a flower shop called Bloomin' Lovely.
- Rani mentioned that the Battle of Hastings was in 1066 and that history was her favourite subject.
- Halley's Comet passes Earth in 1066.
to be added
- Sarah Jane rescued Luke from the Bane; he has lived for a year. (TV: Invasion of the Bane)
- Sarah Jane refers to the mummies she had seen in 1911 while travelling with the Fourth Doctor. (TV: Pyramids of Mars)