Equinox

A reporter visits David Fielding at a psychiatric hospital for a follow-up about the deaths of his three friends. David remains catatonic and lashes out when a photo of Dr. Watermann is shown. In the scuffle, David loses his cross, triggering a frantic reaction that hints at his link to the events.

The reporter listens to tape recordings of police interviews conducted after David was brought to the hospital. The recordings are used to reconstruct the events that drove him insane. The flashback structure reveals the sequence leading to the friends' deaths.

David joins Susan Turner, Jim Hudson, and Vicki in a search for Dr. Watermann through a forest canyon. They find Watermann's cabin destroyed, hinting at a violent past. The tension escalates as they press deeper into the wilderness.

Inside a cave, a cackling old man hands them an ancient book filled with magical lore. The book reeks of sulfur and contains the Lord's Prayer written backwards, described as a veritable bible of evil. The group realizes Watermann's experiments with the book are connected to the danger they've stumbled upon.

They learn Watermann's ritual experiments went awry, releasing a giant tentacled creature that destroyed his house. The revelation shows the true stakes of meddling with dark powers. The group must decide how to proceed.

Watermann appears and grabs the book, with David and Jim giving chase. David tackles Watermann, causing him to strike his head and die; Watermann's body vanishes afterward. The group stands in shock as the supernatural event unfolds.

Asmodeus, disguised as a forest ranger, learns that Jim and David still have the book and sends two monsters—the giant ape-like creature and a green-skinned, fur-clad giant—to retrieve it. The ape-like creature kills the old man from the cave. The danger moves from the forest into the group's immediate circle.

Asmodeus begins to sexually assault Susan, but her cross repels him. After Susan loses the cross, she becomes demon-possessed and attacks Vicki, who cannot stop her. David intervenes, using a mystical symbol from the book that briefly silences Susan.

Asmodeus kills Jim and impersonates him to fool David, who initially believes the imposter. Realizing the trick, David engages in a fight with the demon but is knocked unconscious. Asmodeus then reveals himself in his true form: a winged, red demon.

After killing Vicki, Asmodeus attacks David and Susan; they flee to a cemetery and hide behind a large stone cross atop a grave. The demon flies into the cross and dies, and the cemetery erupts in flames, killing Susan.

A giant shadowy figure prophesies that David will be dead in one year and one day. The ominous warning hangs over him as the nightmare darkens his fate.

David panics and flees to a nearby road, where a driverless car runs him down. A car with two passengers stops to help him, offering a fleeting chance at salvation.

The injuries and trauma push David toward madness, and he is confined to a mental hospital. The haunting memories from the case haunt him as his reality blurs with nightmare.

One year and one day later, an evil-faced, reanimated Susan arrives at the hospital to kill him. Her return confirms that the terror is far from over and the cycle of nightmare may begin anew.