Before Ethan Banning was a down-and-out demon-possessed PI, he was just a down-and-out PI.
Ethan wouldn't normally touch a haunting case. Mostly because he doesn't believe in ghosts. But when Charlie Mullen asks him to spend the night at a supposedly haunted morgue, Ethan figures, why not? He's broke and Charlie's offering double his normal rate, and that's good enough for Ethan.
But when a troublesome ghost really does show up, Ethan realises he's going to need more than a good supply of alcohol to get through the night.