Werewolves. Witchcraft. Wildlife. It's all different in the bayou.

A year after Eli and Dag survived their second encounter with a monster, things are finally going well. Really well—as far as Eli is concerned, anyway. He's lost weight. His energy is up. His hair is on point. There are the little things, like the occasional flare-ups of temper and the urge to murder the kids down the street, but that's just part of living by teenagers. Right?

But when Posey, a man they met the year before, shows up on their doorstep a few nights before Halloween, everything starts to go wrong. Posey needs their help: his boyfriend has disappeared. Worse, his boyfriend might have committed murder. Oh, and even worse? His boyfriend is a werewolf—a special kind native to Louisiana, known as a rougarou.

Eli and Dag begin their search for the missing rougarou, but it turns out, they're not the only ones on the hunt: the mob, a gator-man, an implacable monster hunter, a witch, and a few bonus werewolves are all looking for him too. The rougarou, they learn, is the key to a ritual—a ceremony to summon a lwa, a powerful spirit. As time runs out, Eli and Dag must hurry to find the rougarou before the others. If they're too late, the end of the world might be only the beginning.