The Curious appears on a suburban street at the home of a young boy, Stu.
Stu constantly cheats to get what he wants: including cheating at video games, stealing exam papers from his father (the Deputy Headmaster of Stu's school) to copy the questions, and faking being sick so he can stay home for the day. Whilst in his room "sick", Stu notices an elderly neighbour, Mrs McMurtle, taking a huge delivery of cat food. He spies on her and watches as she opens a false wall in her garage, revealing an enormous bathtub. She heats up the cat food and takes a bath in it; turning into a monster. Stu searches online and discovers that she is a Koekoeken: a creature which takes over human bodies.
Stu tries to tell his mother what's going on, but she thinks he's delirious. She agrees to go over and check it out on the pretext of borrowing a lawnmower. However, when she opens the false wall, Mrs McMurtle has hidden the bathtub. Stu's mother gets an urgent call from her job and has to go into the office, but sends Mrs McMurtle over to babysit. Stu confronts her and she admits she is a Koekoeken, having lured Stu into finding out her secret and faked a phone call to get rid of his mother. The Koekoeken is a parasite which lives for hundreds of years by possessing human hosts. Mrs McMurtle will not live much longer, and the Koekoeken needs a new host - who must be a child. She has chosen Stu because of his cheating and lying.
The Koekoeken tells Stu that she can't forcibly take his body. She has to win it by beating him in a fair game of chance; if Stu refuses to play, she will send a letter informing his school that he has been selling copies of exam papers. He will be expelled, his hard-working sister Kelly will be branded a cheat, and their father will be fired. Stu tries to fool the Koekoeken with a trick coin, but she sees through him and insists he play a card game instead. Stu wins, to the Koekoeken's horror. He demonstrates that he used a hidden camera to show him the cards. However, at breakfast the next day, "Kelly" reveals that she is now the Koekoeken. When the real Kelly learned about Stu's cheating, she agreed to play the game to save him; and the Koekoeken beat her using Stu's own trick with the camera.
The Curious takes a souvenir from Mrs McMurtle's garden: a grave marker at the spot where she had buried one of her cats.
This episode contains examples of:
- Attack of the Killer Whatever: Stu is shown watching a horror movie called Attack of the Killer Flesh-Eating Bananas.
- Bread, Eggs, Milk, Squick: Whilst explaining that she needs the taurine found in cat food to survive, the Koekoeken casually mentions that hundreds of years ago she had to use cow's urine.
- Cheaters Never Prosper: The moral of the story.
- Chekhov's Gun: Subverted with the trick coin - when it comes into play, the Koekoeken already knows Stu has it, and he can't use it.
- Chess with Death: The Koekoeken forces Stu and Kelly into this.
- Cool Big Sis: Kelly.
- Crazy Cat Lady: What Stu thinks Mrs McMurtle is.
- Didn't Think This Through: It didn't occur to Stu that his dad and sister would be in serious trouble if anyone found out about him copying exam papers.
- Downer Ending: Stu has successfully defeated the Koekoeken, only to discover that she has taken his sister's body.
- Even Evil Has Standards: This is why the Koekoeken has to beat someone in a fair game of chance before she can take over their body. However, by the end, this is subverted, given it is perfectly willing to cheat to get back at Stu.
- Evil Old Folks: Mrs McMurtle, who is secretly the Koekoeken.
- Hoist by His Own Petard: The Koekoeken uses Stu's own trick to take over Kelly's body.
- Puppeteer Parasite: The Koekoeken.
- "Rear Window" Homage: Invoked. The Koekoeken knew that Stu likes to spy on his neighbours, and used this to lure him.
- Snooping Little Kid: Stu, who spies on Mrs McMurtle with the aid of cameras.