Marty McGuire, a third-grade tomboy who prefers catching frogs to princess tea parties, gets a huge disappointment. Her class project isn't about dinosaurs or animals—it's a 'Save the Earth' contest. Marty's team is assigned worm composting, which she thinks is boring and gross. But as she learns how worms turn food scraps into rich soil for the school garden, Marty discovers that science can be messy, surprising, and full of squirmy, wriggling fun.