Jenny is locked out of Sarah's room because she made a mess in it when she was young. SPOILER: After she dreams that she is tall enough to reach the lock, she discovers that she really is. She is playing carefully in Sarah's room when Sarah finds her there. But when she and their mother realize that Jenny is careful, they allow her to be there and her mother even gets wallpaper for Jenny's room; she wasn't considered responsible enough before.

The final verse reflects the first. The dream sequence is sweet. Sarah and her mother could have reprimanded Jenny for disobeying; fortunately, they are open to change and growth.

The illustrations are typical Sendak, which is to say, wonderful.