Millie is twelve years old, and she is a schoolgirl detective. Dave is her younger brother, and in this story he has been bullied out of his new, expensive trainers. It's up to Millie to find out what's happened, maybe together with his best mate Joe, and help Dave to put it right. Even if it means facing up to Badger, the school bully. Their dog Boris has a sensitive nose and can sometimes help, too. But even so, can Millie and Joe sort it out? Will Badger give up without a fight? And where did that sparkling diamond ring come from?