The good news is that the third grade can buy a class pet. The bad news for Rosemary is that the kids want a rat! How gross!

There's no way Rosemary's mother will let her take a turn as ratkeeper for a creepy, dirty animal. But Rosemary surprises herself when she begins to like Cheese, the gray and white hooded rat. Then, when Cheese's life is in danger, it's Rosemary to the rescue . . . if she can hide him from her family!