The film begins with a new beginning similar to the first film. Ash Williams and his girlfriend, Linda, take a romantic vacation to a seemingly abandoned cabin in the woods. While there, Ash plays a tape recorder from the cabin's previous inhabitant Professor Knowby. The tape features Knowby reciting passages from the Necronomicon Ex-Mortis (or Book of the Dead), which he has discovered during an archaeological dig. However, the recorded incantation unleashes an evil force which kills and later possesses Linda, forcing Ash to decapitate his girlfriend with a shovel when she attacks him, he then buries her.
Five Michigan State University students, Ash Williams (Bruce Campbell) and his girlfriend Linda (Betsy Baker), accompanied by Ash's sister Cheryl (Ellen Sandweiss), their friend Scotty, and his girlfriend Shelly , venture into the Tennessee hills to vacation in an isolated cabin for their spring break. They soon run into trouble, first narrowly avoiding another motorist, then having a sudden scare as the bridge near the cabin begins to collapse as they cross. That night, while Cheryl is making a drawing of a clock, her hand becomes violently possessed by a mysterious entity, causing her to draw a picture that looks like a deformed, evil face. She fails to mention the incident to the others, dismissing it as her imagination.
At University of Zurich Institute of Medicine in Switzerland, Herbert West brings his dead professor, Dr. Hans Gruber, back to life. There are horrific side-effects, however; as West explains, the dosage was too large. When accused of killing Gruber, West counters: "I gave him life!"
The film adheres very closely to Lovecraft's story, but there are a few changes. The sailors aboard the Emma first encounter the Alert abandoned at sea, rather than crewed by Cthulhu cultists and taken over by Emma 's crew after a violent confrontation as in the original story. Additionally, the film depicts the narrator present at the time of his great-uncle's death, who dies peacefully in his sleep, rather than being summoned upon the mysterious death of his great-uncle, who was presumably killed by Cthulhu cultists in the original short story. The narrator (Matt Foyer) notes as well that Inspector Legrasse, who had directed the raid on cultists in backwoods Louisiana, had died before the narrator's investigation began.
In the underground Facility, senior technicians Gary Sitterson and Steve Hadley discuss plans for a mysterious ritual. A similar operation undertaken by their counterparts in Stockholm has just ended in failure.
In 1765, the inhabitants of the town of Arkham are suspicious of the strange phenomena surrounding the grand "palace" that overlooks the town. They suspect its inhabitant, Joseph Curwen, of being a warlock.
Dr. Edward Pretorius (Ted Sorel) is a scientist who has developed the Resonator, a machine which allows whoever is within range to see beyond normal perceptible reality. His assistant, Dr. Crawford Tillinghast (Jeffrey Combs), activates the machine and soon sees strange creatures in the air. When he is bitten by one of them, he urges Pretorius to turn the machine off. However, the crazed Pretorius refuses. Events transpire to the point where Crawford panics, fleeing outside. When the police arrive, they find Pretorius decapitated. Crawford is subsequently arrested and accused of murder.
For the first two acts, the plot essentially follows the lines of the short story. However, in the third act of the film, the protagonist, Wilmarth, uncovers an attempt by collaborators (or cultists) to open a gateway between Yuggoth and Earth. He foils the plot with the help of an added character, Hannah, the child of one of the collaborators. His escape, however, is unsuccessful and at the end of the film the audience discovers that Wilmarth has been narrating from a machine attached to the cylinder in which his brain now resides. This differs from the original story in which Wilmarth flees in the middle of the night and safely returns to Arkham.
Ward stars as 1948 hardboiled private detective H. Philip Lovecraft, in a fictional universe where magic is real, monsters and mythical beasts stalk the back alleys, zombies are used as cheap labor, and everyone—except Lovecraft—uses magic every day. Yet, cars, telephones and other modern technology also exist in this world.
In the 1920s, impoverished horror writer Randolph Carter rents a room from Mrs. Caprezzi, an elderly land lady. Not long after settling into the shabby and almost bare room, he discovers a pool of ammonia on the floor that has leaked down from the room above. Mrs. Caprezzi, while cleaning up the ammonia, regales Randolph with strange stories of Dr. Muñoz (Jack Donner), the eccentric old gentleman who lives in the room upstairs. Later, Randolph suffers a heart attack and painfully makes his way to the doctor's room where he is treated with an unconventional medicine and makes a remarkable recovery. Befriending the doctor, Carter soon discovers the awful truth about the doctor's condition, why his room is kept intensely cold, and the fragile line that separates life and death.
Two romantic couples, consisting of four teenagers, decide to spend a weekend together located in a remote cabin found in the woods. An unseen force stalks and watches the group without their knowledge. Ellen (Ellen Sandweiss) and her boyfriend Bruce (Bruce Campbell) enter the woods to have a picnic lunch. The other couple, Scotty (Scott Spiegel) and Shelly (Mary Valenti), remain at the cabin playing Monopoly to pass time. During their lunch, Bruce announces to Ellen that they're camping on an Indian burial ground. Ellen is concerned, but Bruce assures her that they will be fine as long as they don't disturb the graves of the dead. Bruce then explores the area and discovers an ancient dagger belonging to the Indians. Ignoring his own advice, he takes the dagger with him.
Eight months after the events of Re-Animator, Doctors Herbert West and Dan Cain are working as medics in the middle of a bloody Peruvian civil war. In the chaos of battle and with plenty of casualties to work on, they are free to experiment with West's re-animation reagent. When their medical tent is stormed by the enemy troops, West and Cain return home to Arkham, Massachusetts. There, they resume their former jobs as doctors at Miskatonic University Hospital, and West returns to the basement laboratory of Cain's house to continue his research.
Claire Ward (Sibbett) hires private investigator John March (Terry) to look into the increasingly bizarre activities of her husband Charles Dexter Ward (Sarandon). Ward has become obsessed with the occult practices of raising the dead once practiced by his ancestor Joseph Curwen (Sarandon in a dual role). As the investigators dig deeper, they discover that Ward is performing a series of grisly experiments in an effort to actually resurrect his long-dead relative Curwen.
The film opens with a dream sequence in which stock market tycoon Paul Marsh discovers a mermaid with razor sharp teeth while scuba diving into a carven pit. Paul awakes on a boat off the shores of Spain, where he is vacationing with his girlfriend, Barbara, and their friends Vicki and Howard. A sudden storm blows their boat against some hidden rocks. Vicki is trapped below deck, and Howard stays with her while Paul and Barbara take a lifeboat to the nearby fishing village of Imboca. During their absence, an unseen creature from the deep attacks the two in the boat.