Would-be detectives Trevor, Nick and Robyn are hot on the trail of a sandwich thief when they learn that more than food has been going missing at school. A valuable hockey book has been stolen from the library, and the kids worry that the librarian might lose her job if it isn't found. Who would steal a hockey book? Could it be Robyn's arch-nemesis and hockey enthusiast Cray? Or could it be Ms. Thorson, the Oiler-fan and teacher? The kids are determined to solve these mysteries even though their sleuthing efforts land them in trouble at every turn.