Milly is having her new monster friends over for a sleepover—the trouble is, her perfect sister is having her human friends over too, in a third terrifyingly terrific tale

When Maud's perfect twin sister, Milly plans a sleepover, their mother forces Maud to have her friends over too. What can possibly go wrong? Nothing much—just that Maud's family might find out about Rotwood High being a school for real monsters! As if that's not enough to worry about, Maud is tricked into looking after Violet, the school hamster, by her arch enemy, Poisonous Penelope. But Violet is no ordinary hamster! She's a pedigree vampster and an expert cage-breaker. With a vampster on the loose, sleep is the very last thing that happens!