Under the guidance of an Aleister Crowley disciple, an elite group's leader unleashes a supernatural entity that begins to consume the village of Marienbad and its residents. In an effort to contain the menace, the nearby mayor proposes a dam to flood the valley, sealing the dark force beneath the water. Unfortunately, fate intervenes, allowing the leader to escape as the village is submerged. Four decades later, a series of bizarre disappearances and deaths plague the town adjacent to the reservoir, raising suspicions that the malevolent presence has returned to wreak havoc once more.