Ever since his mentor—the original Demonkeeper— mysteriously disappeared, Nat has been in charge of the demons that live in his house. Most of them are just nuisances, but the Beast who lives in the basement is very dangerous. When Nat goes out one night, a clueless burglar breaks into the house and unwittingly sets the Beast free. Meanwhile, a vicious villain, the Thin Man, wants to use the Beast for his own evil purposes. Can Nat defeat the Thin Man and return the Beast to the basement without any major casualties?