One of the Moomins' favorite foods is pumpkin pie—and when the pumpkin plants in Moominmamma's garden grow bigger leaves than fruit, the family walks around with sad faces. However, Mr. Hemul has grown a plant that, if his promises are to be believed, produces the largest pumpkins. Moominmamma doesn't let anyone in on the secret of Mr. Hemul's cultivation. But what can she do when she finally realizes that the pumpkin in her garden won't stop growing?