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 Boomerang: The trick coin in the end. It appears to be used in the Koekoeken and Stu's standoff where Stu can't use it, but it comes back when the Kokoekoeken plays Kelly and beats her using it.
- 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 into this, then Kelly when Stu cheats her.
- Cool Big Sis: Kelly.
- Crazy Cat Lady: What Stu thinks Mrs McMurtle is.
- Death by Origin Story: The Koekoeken has stolen the bodies of many young children over time, long since Stu was born. She explains that when she acquired the body of Mrs McMurtle it was younger than Stu. As well as stealing the bodies and then occupying them, it’s never mentioned how she gets the souls of her victims out of their bodies, but even if she steals the body in a non-violent way, then the victims still dies.
- 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.
- Fictional Document: The website that provides information on the “mythical” Koekoeken. It allows the viewer to understand what’s going on, without an intrusive infodump in the dialogue.
- Hoist by His Own Petard: The Koekoeken uses Stu's own trick to take over Kelly's body.
- Hypocrite: The Koekoeken gets angry with Stu for cheating, but shows a willingness to do so itself. Not only does it win against Kelly using the same cheat that Stu used against it, but it also breaks it's own rules by selecting the second game instead of letting Stu pick a new one of his own. Granted, it had just caught him trying to rig the game in his favor, but still.
- Ironic Echo: "It isn't cheating, right, Duck? It's simply winning without the pain."
- Meaningful Name: Koekoeken is Dutch for “cuckoo”, a family of birds popularly known for its brood parasitism. Except that the Dutch word is "koekoek" and the plural is "koekoeks".
- 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.
- Sadistic Choice: The Kokoeken forces Kelly into a game for her body to prevent her telling the school about Stu's cheating.
- Snooping Little Kid: Stu, who spies on Mrs McMurtle with the aid of cameras.
- Voices Are Not Mental: Although the Koekoeken briefly speaks in the voice the Koekoeken’s last victim had, she was doing this on purpose. Before and after the line where the Koekoeken speaks in Kelly’s body, she sounds just like Kelly. Weather this is intentional or just how it works when the Koekoeken conquers a new body is unknown.
- Wham Line: Kelly calls Stu "Duck", revealing that the Koekoeken succeeded in claiming a new body after all.
