In an ancient Irish forest, three witches live in an hoary cottage, guarding an underground temple to their evil god Pan. Occasionally, they abduct residents of the nearby town of Dunsmir, to offer their victims soul in exchange for forbidden knowledge. This is accomplished through the use of a dream-drug, which allows them to contact their sleeping victim, and cause him/her to sleep-walk into the forest, where they are captured and taken to the cottage.
The scenario begins with an investigator beginning to experience terrible nightmares involving a horrible witch appearing in their dreams. Over the course of three months, these nightmares increase in intensity, until, one night, the victim awakens to find that the horrible witch is actually in their bedroom, leaning over them. She takes them by the hand, and slowly leads them down the stairs, through the deserted streets, and into the forest.
When they reach the cottage, the three witches lead them, through a trap-door in the floor, down 555 glowing red steps, into the Temple of Pan, where he is sacrificed to the dreadful deity. All this, unless the investigators can stop it.
From the midst of ordinary but unsettling dreams, the investigator feels the intrusion of a probing foreign consciousness, which calls their name from a distance, beckoning them with the promise of forbidden knowledge.
Suddenly, the dreamer finds himself by a stonework gate on the edge of a forest at night, looking into the face of the hideous witch, while squawking crows circle around. The witch takes the dreamer by the hand, and, when they enter through the gate, the dreamer awakes, terrified. He is aware that the dream really happened.