Millie is strong. Millie is fierce. But Millie has learned to keep her fierceness in check. And since she's been sweet all summer long, Millie gets to have a sleepout with her friends. One where she promises to be well behaved. But things don't go as Millie planned, and our fierce little heroine is not happy. Still, she tries her best to keep her fierceness inside. But when the scary dog from next door howls at the girls' tent, Millie's ferocity saves them all!