Claudia's sister is mean! She's too busy being smart to be nice. Even Claudia's grandmother, Mimi, can't get close to Janine. Plus, Mean Janine puts down the Baby-sitters Club. And that makes Claudia MAD!
This summer the members of the Baby-sitters Club are starting a play group in the neighborhood. Claudia can't wait for it to begin. But then Mimi has a stroke...and the whole summer changes.
Now Claudia has to spend her time "Mimi-sitting" instead of baby-sitting. And things with Janine are going from bad to worse. One of the Kishi sisters has to start being nicer. And it's sure not going to be Claudia!