«The Lurking Fear» by Howard Lovecraft

The narrator, hearing tales of a “lurking fear” upon Tempest Mountain in the Catskills, takes two men with him to investigate. They camp inside the deserted Martense mansion as a lightning storm approaches, and feeling strangely drowsy, they all fall asleep. The narrator wakes up to find both his companions missing, and in a flash of lightning sees a demonic shadow cast upon the fireplace chimney from a grotesque monster like the other one.