It's a dark and stormy night. Your car breaks down on a lonely road, and so you look for shelter at the forbidding old mansion on the hill. At the door, a gaunt, cadaverous butler leads you inside, where a strange assortment of individuals are gathered for the reading of the previous occupant's will: a hypnotist, an egyptologist, an occult investigator, a fraud medium, a wisecracking reporter; but could one of them be the notorious criminal known as the Crimson Bat? Not long after, a detective arrives in search of a madman who escaped from the local insane asylum. In the basement, a mad doctor performs grotesque experiments. Rumors circulate of a family curse, and of strange creatures that roam the moors by night. Secret passages abound. Someone is murdered by a trained gorilla, another suggests holding a seance. Imprisoned in the attic, a madwoman plays cacophonous dirges on an old pipe organ. Down in the cemetery, a hooded figure breaks into the old mausoleum by the light of a black candle. A dead body turns up in a wax museum. A scream is cut short by a clawed hand closing over your mouth, as you realize that the detective investigating the case is really a werewolf...

(In other words, the literary equivalent of an early-to-mid 20th century gothic horror/mystery b-movie)