Music is bad for you; Lorna Periwinkle knows this. Five years ago she accidentally summoned a shadow fiend with her father’s violin, on a day when she disobeyed the rules and saw her father swallowed by the creature that she summoned. Now, as she approaches her thirteenth birthday, it seems that something new is in the air. Even Lorna’s indomitable mother is nervous. It turns out that the shadow fiend her father banished isn’t gone forever. In fact, it’s coming back at midnight on the day she turns thirteen.