Harriet is doing odd jobs round the nursery and Timmy is eager to help out. He finds a yellow beret (the closest thing he can find to Harriet's yellow hard helmet) and a toy tool belt and begins his round of odd jobs. Unfortunately his attempts at mending his friends' toys result in disaster: a wheel falls off Mittens' hobby horse, Ruffy's robot breaks and Ruffy's remote control car just grinds to a halt. Finally Harriet takes matters into her expert hands, and together her and Timmy make amends. Timmy learns how to mend things the right way with the right tools, and Harriet rewards him with a proper yellow hard hat of his own.