Assembly Day at St. Catherine's dawns bright and cloudless as professional woman gather from all around Ohio to talk to the schoolgirls about their careers in medicine, at NASA, and as yoga instructors. Administrative assistant Jazz Ramsey is involved herself, giving the girls a taste of her lifelong passion: cadaver dog training. Her adorable new puppy Wally hasn't been certified yet, so she borrows the fully-trained Gus from a friend and hides a few bones in the unused fourth floor of the school for him to find.
The girls are impressed when Gus easily finds the first bone, but for the second Gus seems to have lost the scent, and heads confidently to a part of the floor where Jazz is sure no bones are hidden—at least not any that she's put there. But Gus is a professional, and sure enough, behind a door that shouldn't have been opened in decades, is a human skeleton.
Jazz recognizes the skeleton as Bernadette Quinn, an ex-teacher at the school who'd never returned after one Christmas break, though letters and postcards from her had seemed to indicate there was no cause for worry. But now it seems Bernadette never left the school at all, and her hiding place makes it clear: this was murder.
Bernadette's strident personality means there are a plethora of suspects inside the school and out of it, and as Jazz gets closer to the truth she can't help but wonder if someone might be dogging her footsteps . . .