A boating accident off the coast of Spain sends Paul and his girlfriend Barbara to the decrepit fishing village of Imboca. As night falls, people start to disappear and things not quite human start to appear. Paul is pursued by the entire town. Running for his life, he uncovers Imboca's secret..they worship Dagon, a monstrous god of the sea...and Dagon's unholy offspring are on the loose...

Studying under a disciple of Aleister Crowley, the leader of an upper class group invokes a supernatural force that slowly devours the village of Marienbad and its inhabitants, threatening to spread beyond its geographical limits. The mayor from the town nearby commissions the building of a dam which would flood the valley and therefore submerge the village forever sealing the evil force under water after leader and his followers were incapacitated to be kept from escaping. However, fate ensured the leader's freedom as he remained in the depths when the waters covered Marienbad. Now 40 years later an array of disappearances and deaths in mysterious circumstances are threatening the town next to the reservoir that now covers Marienbad.

Mommy's boy Juantxo is engaged. Dragged to the party by his friends Konradin and Paco, he loses his expensive wedding ring inside the body of a prostitute. Mafioso whorehouse owner Villambrosa finds the ring. Meanwhile Villambrosa's rival gangster Souza sends femme fatale Fatima to check things out. Juantxo and his friends are trying to get the ring back and in the process get involved in the war between gangs.