On her way to Auntie Alice's house, Miffy finds a caterpillar. She brings it over to her Auntie, who tells her that something magical will happen if Miffy visits her every week and feeds it. So, that's what she does, but nothing happens! One day the caterpillar is suddenly all covered up. Is it ill? But then Miffy discovers the magical change that takes place. One morning, the Bunny family has no carrots left. Miffy goes over to Poppy Pig's for some, but she has just eaten her last one. Just then Auntie Alice passes by, and invites Miffy to an exciting carrot party! All the friends are invited, and by the end even Boris and Barbara Bear love carrots!