In 1968, in Hunter's Point, California, a tragic encounter occurs when the infamous Zodiac Killer claims the lives of David Arthur Faraday and Betty Lou Jensen on Lake Herman Road.
Fast forward to the present day in Virginia, where Mick Bradley, a struggling landscaper, takes a chance on improving his financial woes by purchasing an abandoned storage locker alongside his pawnbroker friend Harvey. Within the locker, they uncover a chilling find: home movie reels depicting the Zodiac murders filmed by the killer himself. After some initial reluctance, Mick's wife Zoe decides to assist in the investigation, hoping to secure a $100,000 reward for any information that might lead to the Zodiac’s arrest.
As their investigation unfolds, danger encroaches when the Zodiac captures Tina, the manager of the storage unit facility, brutally slitting her throat. Driven by urgency, Mick and Zoe break into the storage facility office to unearth the identity of the individual who rented the Zodiac locker, ultimately discovering the name Betty Ferguson. This leads them to confront a mysterious figure lurking in the shadows outside.
Receiving a warning from his trailer park neighbor Ray about the peril of pursuing Zodiac, Mick pushes forward with Zoe and Harvey. They infiltrate the residence of Betty Ferguson and her husband Balthazar, only to be confronted at gunpoint by their son Benjamin Ferguson. Benjamin, revealing that his elderly parents reside in Florida, provides Harvey with a business card indicating he works as an editor at the Tri-County News Ledger. As they depart, a neighbor inquires if everything is alright, raising the stakes of their trespass.
Amid their relentless quest, Harvey stumbles upon a cipher key while examining one of the film reels. This discovery positions him to decode the infamous Zodiac cipher, while Zoe delves into town hall records to investigate Benjamin’s background. She uncovers startling parallels between Benjamin’s history and Zodiac, establishing links to San Francisco in the 1960s, particularly post-Vietnam War. Yet, Benjamin had since relocated to Virginia, pursuing theories suggesting that Zodiac was shifting eastward during the murder of cab driver Paul Stine.
Despite the disarray of facts, Mick becomes increasingly convinced that Benjamin is the Zodiac. Zoe grows concerned as Mick's increasingly erratic behavior leads him down a path of paranoia, especially when they find Harvey has gone missing—a presumed abandonment in pursuit of the reward.
In a frantic search, Mick investigates the area above their pawnshop and discovers a gruesome sight: Harvey's murdered body. Meanwhile, Zoe tracks Harvey's van, only to unwittingly lead herself into the clutches of the Zodiac. A menacing call from Zoe's phone escalates the tension as Zodiac taunts Mick, threatening him to refrain from involving the police.
With Zoe captured, Zodiac reveals his chilling rationale: he had not killed in 40 years, having once followed Benjamin from San Francisco, knowing that he was close to unraveling his identity. It was the negligence of his locker payments that reignited his psychopathic tendencies.
The gripping conclusion arrives as Mick confronts Zodiac at a remote farm. In an electrifying clash, Mick bravely fights to rescue Zoe, leading to a fierce showdown across the farm. Ultimately, after a tense struggle, Zoe manages to subdue Zodiac, allowing Mick to shoot him in the throat.
Four weeks later, as the investigation continues into the recent spate of murders, Mick mysteriously disappears while fixing a light outside their trailer. When Zoe expresses concern, an unsettling shadow looms in the background, leaving their fate uncertain.
