Dagon

Paul Marsh dreams of encountering a mermaid with razor-sharp teeth while exploring an underwater cave. He wakes on a boat off the shores of Spain with Barbara and friends Vicki and Howard. A sudden storm drives the vessel toward rocks, pinning Vicki against the bed and flooding the cabin.

A violent storm drives the boat toward rocks, forcing Paul and Barbara into a lifeboat bound for Imboca. An unseen water creature attacks Howard and Vicki back on the wreck, leaving their fate uncertain. The survivors press toward land as the sea roils around them.

Paul and Barbara reach the seemingly deserted fishing town of Imboca and seek aid for Howard and Vicki. They reach a church where a priest agrees to help them. Two fishermen at the docks volunteer to take one of them back to the boat; Paul goes with them while Barbara stays to find a phone.

Barbara remains behind to call for help, hoping to contact their missing friends. Paul accompanies the fishermen back toward the wrecked boat. The town grows eerier as night falls and danger seems imminent.

Paul goes to the hotel where Barbara supposedly stays, but she isn’t there. He waits in an old, filthy hotel room and is haunted by another mermaid dream. He is awakened by a looming crowd of fish-like villagers approaching the hotel and flees.

Paul hides in a tannery after fleeing the hotel, where he discovers Howard's skinned corpse. He escapes the tannery by starting a fire and finds momentary safety with Ezequiel, the town's last full-blooded human.

Ezequiel explains that years earlier Captain Orpheus Cambarro led Imboca to worship Dagon, replacing the Catholic Church. Prosperity came from offerings of fish and gold, but Dagon demanded blood sacrifices and breeding. Over time the village dwindled, leaving only half-fish descendants who abduct visitors to breed or sacrifice to Dagon.

Paul pleads with Ezequiel for help escaping. They head to Xavier Cambarro's manor to steal the town's car. Paul tries to hot-wire it but accidentally honks the horn, drawing attention. He encounters Uxia, the mermaid from his dreams, who saves him but he is horrified to find she has tentacles. He escapes and crashes the car in a frantic attempt to flee.

Paul is captured and thrown into a barn, where he is reunited with Vicki, Ezequiel, and Barbara. They plan to escape, but the traumatized Vicki, having been impregnated by Dagon, kills herself.

Paul and Ezequiel are chained in a butchery and offered one last chance to worship Dagon; they refuse. Paul apologizes to Ezequiel, who thanks him for helping him remember his parents. The cult flays Ezequiel alive as the captives recite the 23rd Psalm together.

Uxia talks down the cult and saves Paul. He offers to stay for Barbara's release, but Uxia insists Barbara must bear Dagon's child. She then orders the priest to make arrangements for their marriage.

After Uxia leaves, Paul turns on the guards and the priest and escapes from the inner chamber. He presses toward the church, aiming to reach Barbara and end the nightmare.

Paul reaches a hidden passage that leads to an underground ritual chamber where a congregation watches a ceremony unfold. Uxia presents Barbara, naked and handcuffed to a trapeze, and lowers her toward a pit that opens to the sea.

Paul sets several cultists on fire and tries to rescue Barbara from the pit, but she begs to be released because she is pregnant. He cannot untie her without the key, and two tentacles emerge from the water to drag Barbara down, leaving only her severed hands on the trapeze.

Xavier Cambarro appears as a monstrous Imbocan; Uxia explains Paul's true parentage and that his mother escaped Imboca years ago. Paul learns he is Xavier's child, and Uxia declares he will be her lover as they dwell with Dagon and Barbara. Paul, now gilled, embraces his fate and dives with Uxia into Dagon's undersea lair.