Jimmy Zest is an inventor and, he likes to think, the brains of his class. The trouble is, nobody knows what idea will come to him next and which of his friends - Gowso, Mandy, Penny Brown, Knuckles, Shorty or Legweak - will be persuaded to join in the mayhem. Five great stories in which Jimmy, sometimes with the help but often the hindrance of his mates, has a horror with horse hair, uncovers fowl play in the park, causes chaos on the school trip, trails a tortoise and loses a teacher.