The Hatford boys' New Year's resolution is "the girls can stay . . . but only if they play by our rules." Their mother insists that they "treat those girls as though they were your sisters." Okay, but somehow the boys' interpretation owes more to sibling rivalry than to brotherly love. The one weak link is young Peter, who doesn't understand the rivalry, openly likes the girls, and sees nothing wrong with sitting in their kitchen eating homemade cookies...

Once again the Hatford brothers and the Malloy sisters find themselves pitted against each other when embarrassing pictures of the boys turn up in the girls' basement, and the boys try to figure out how to get them back.