From the bestselling author of the generation-defining series The Baby-sitters Club comes a series for a new generation!

It is a big mystery.Karen can do lots of great tricks with her new yo-yo. But when she takes it to school to show her friends, the yo-yo shows Karen a brand-new trick. It disappears! It is not magic. Somebody has taken Karen's yo-yo. And Karen is going to figure out just who the meanie-mo is.