The mystery of the haunted dance hall

"Bee is reluctantly attending Camp Blue Heron over the summer while her mother teaches a summer course. Bee doesn't make friends easily, but she feels an immediate connection to a fellow unusual camper called Zippy who lets her in on a mystery: every night the teenaged girls in the Hawks cabin are given fresh batteries, but in the morning the batteries are all dead! The girls are supervised and there's no evidence that they snuck out the door, bu...