“Open the windows. This heat is almost as unbearable as the stench.”

On the cracked rotting wooden floor in the center of the mansion’s entrance hall were seven mutilated human bodies. The room was an ancient canvas with dried globs of black-red paint rotting on the surface.

The bodies were arranged as a star, and a pentagram had been painted with their remains. There was a body for each point of the star, and one last body in the center. A circle, painted with blood, enclosed the...