Maud Blunder is just an ordinary seven-year-old girl living in Greenton, until she sees a horrifying troll, called Borisulator Treecruncher, climb in through her bedroom window.
Borisulator, who is built like a potato filled with rocks and smells like grated earwax smothered with sauce made from bones, sings a song about making little girls into burgers.
Maud tricks the troll into falling out of her window by telling him that there are child-brain lasagnes outside. She realises that the troll has to be stopped before he eats any more children and sets to work trying to invent a trap.
Meanwhile, in a cave just outside Greenton, Laurengross Eversogrim starts to suspect that eating children is wrong, and grows tired of hunting with her fellow trolls. She decides to live as a vegetarian.
After a brief misunderstanding involving an eyebrow and lashings of ketchup, Maud and Laurengross team up to stop the trolls, using a catapult that fires peas. They lure the trolls by creating a big mound of skunk trainers.