Within the Woods is a 1979 horror short film written, directed and edited by Sam Raimi. Raimi drew inspiration from his earlier short film Clockwork, deciding to produce a proof of concept horror film to help build the interest of potential investors. Raimi cast his friends Bruce Campbell and Ellen Sandweiss as the two protagonists and produced the film for $1,600. Shot on location in a remote cabin in the woods, production was a difficult process because of the low budget. Several of the special effects presented in the film were done in a severely low budget manner, some of which were improvised on set. The film centers around demonic possession and mysterious forces originating from the woods.

Raimi convinced a local theater manager to screen the film alongside The Rocky Horror Picture Show, which sparked minor interest. Initially a meager success, the film screened well to test audiences and became the basis of a larger budget remake titled The Evil Dead (1981). The film was the first in the Evil Dead franchise, and launched the careers of both Bruce Campbell and Sam Raimi. Several of the aesthetic qualities found in Within the Woods later defined Raimi's films.

Two romantic couples, consisting of four teenagers, decide to spend a weekend together in a remote cabin in the woods. An unseen force stalks and watches the group without their knowledge. Ellen and her boyfriend Bruce enter the woods to have a picnic lunch whilst the other couple, Scotty and Shelly, remain at the cabin, playing Monopoly to pass the time. During their lunch, Bruce tells Ellen they're camping in 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. While exploring, he finds a dagger in one of the graves. Ignoring his own advice, he takes the dagger with him.

After lunch, Ellen takes a nap. When she awakens, she finds Bruce missing and wanders into the woods to look for him. To her horror, she finds Bruce's dead body, horribly mutilated with apparent knife wounds. She is then startled by a demonic entity hiding in the woods and quickly runs back to the cabin. While fleeing, she is attacked by unseen forces. Running back to the cabin, she screams to be let in and bursts through the door just as the entity closes in. Ellen tells her friends that Bruce has been murdered, but Scotty dismisses the whole thing as a joke and goes to find Bruce. Shelly and Ellen are concerned when Scotty doesn't return right away. Shelly heads out to search for the missing men, but a possessed Bruce assaults and strangles her, eventually stabbing her in the neck and killing her with the dagger that he found, moaning, "Join us."

Ellen encounters her possessed friend and locks herself in another room after grabbing some kitchen knifes. Something attempts to enter the room where Ellen is hiding, and she blindly lashes out with a knife, mistakenly stabbing Scotty, who had just returned to the cabin. Ellen is then attacked by the possessed Bruce, but manages to trap him outside, stabbing his hand several times in the process. The bleeding Scotty tells Ellen to look into the cellar for the gun they brought along. While walking down, she trips on a broken step and injures herself. After finding the gun and going back up, she discovers that Scotty had been stabbed to death by the possessed Bruce; when he tries to grab her by the throat with his injured hand, she cuts it off.

Enraged, the possessed Bruce beats her and puts his other hand around her throat. While being strangled, Ellen picks up Bruce's mutilated hand, still clutching the dagger from before, and uses it to stab him. Gushing blood, Bruce lies motionless for a moment but then gets up and resumes his attack. Ellen grabs a wood axe from the stove and hacks at his body, eventually severing all of his limbs. Severely disturbed by the things she has witnessed, Ellen rocks back and forth, muttering to herself. The corpse of Scotty suddenly springs up, before turning towards the oblivious Ellen, ready to attack. The screen then cuts to black, leaving her fate ambiguous.

Before the development stages of Within the Woods, Sam Raimi and Bruce Campbell were long-time friends who had grown up together. The duo had produced several low-budget films with Super 8 film during their youth. During the early parts of Raimi's career, he directed films that were mostly classified as comedies, such as Booby Bartenders, Shemp Eats the Moon and The Great Bogus Monkey Pignut Swindle. While those films were described as "goofy" and primitive by members of the cast and crew, Raimi eventually produced the short film It's Murder!, which featured mostly comedic moments. One of the sequences of the film involved a suspenseful moment where a criminal jumped on an unsuspecting individual. Raimi later dismissed the short film, but complimented that scene, stating that it was "the only part of It's Murder! that really worked well.

While working on the film, it inspired Raimi to approach the horror genre with more enthusiasm, leading to the conception of his next short film Clockwork. The film featured a woman being stalked by a demented man, and launched an interest in Raimi to pursue working on more horror films. While both Raimi and Campbell expressed a positive opinion on the genre, they admitted they had little experience with the genre and went to drive-in theaters to research various science fiction and horror films. Raimi developed the motto "the gore the merrier" during these sessions at the drive-in, and quickly developed an interest in films featuring high levels of blood. Raimi gained an appeal in B movie cinema, which led him to want to pursue the production of a more ambitious film for his next project. In order to gain the interest of producers, Raimi and Campbell set out to produce a "prototype" film that would serve as a showcase of their talents. The film would work as a trailer to help promote further cinematic productions.