The Creed family relocates from the bustling city of Chicago to the quiet and seemingly peaceful town of Ludlow, Maine. They soon become acquainted with their elderly neighbor, Jud Crandell, who introduces them to a peculiar and isolated burial ground for pets, humorously misspelled as “Sematary,” located just behind their new abode.
As fate would have it, Louis Creed, the father figure, is at the University of Maine one day when he encounters a grave situation involving a young student named Victor Pascow. This unfortunate individual is brought in with devastating injuries following a terrible car accident. Tragically, he dies, but not before he ominously warns Louis by name about the sinister pet cemetery. That very evening, in what appears to be a dreamlike visitation, Victor returns to caution Louis about the dark implications of the burial ground lurking beyond the pet sematary. Louis is jolted awake to find the unsettling evidence of dirt covering his feet.
The quiet life of the Creed family is shattered when Church, the beloved pet cat belonging to Louis' daughter Ellie, meets a grim fate at the hands of a passing truck while the family is away in Chicago. Jud Crandell offers his assistance to Louis, leading him to the Micmac Indian burial ground—a place of ancient rituals and disturbing secrets—where he clandestinely buries Church. While Louis wonders about the fate of a human buried there, Jud, in a state of disbelief, exclaims, “Christ on His throne, no! And whoever would?”
Church returns, but not as the loving companion he once was; he emerges as a grotesque shadow of his former self, bringing chaos with him. The atmosphere becomes even more dire when, a season later, tragedy strikes again. Louis' young son Gage is killed in a similar accident, leaving the family enveloped in unimaginable grief, especially Rachel, Louis' wife, who struggles to cope with the horror of their loss. Compounded by the tension with Rachel's father Irwin, who directs his anger towards Louis, the family's emotional state deteriorates.
In a moment of desperation, Louis contemplates a grave decision: to inter Gage in the cursed Micmac ground. However, Jud Crandell pleads with him to reconsider, sharing the chilling tale of Timmy Baterman, a soldier whose return from death wreaked havoc upon the town after his father buried him in the haunted depths of that very burial ground.
To relieve the family's aching sorrow, Rachel plans a trip to Chicago with Ellie, imploring Louis to join them. Reluctantly, he stays behind and, tormented by visions of Gage, decides to exhume his son’s body from the cemetery. As he traverses the graveyard, he is met once again by the spirit of Victor Pascow, who desperately warns him not to follow through with his decision.
Meanwhile, Ellie dreams of dire omens, telling her mother that "Paxcow" warned her of Louis’s impending actions, creating a sense of urgency for Rachel, who reaches out to Jud. Despite his warnings, Rachel can't shake the feeling of danger and heads back home, only to discover Louis' horrifying intentions.
The darkness deepens when Louis digs up Gage and lays him to rest in the cursed burial ground, ignoring the warnings. Chaos ensues when Gage returns, not as the innocent toddler he once was, but as a malevolent version of himself, leading to the tragic death of Jud and culminating in a series of nightmares as Gage confronts his mother.
Rachel discovers her son in a ghastly twist of fate as he shows her a tool of violence that had belonged to Louis, leading to her demise. Louis, engulfed in despair, realizes too late the horrors he has unleashed. In an attempt to end the nightmare, he uses mortuary methods on Gage, only for tragedy to follow him as he ignites the house in flames, determined to cleanse the evil.
As the flames consume the memories of his family, Louis believes he can achieve a reunion with Rachel, which results in a chilling final confrontation. The screen fades to black as Rachel returns, marred by death, ending in an unimaginable act of violence as Louis is left screaming in despair as the darkness consumes him once and for all.
