While Scott and Annie are exploring a property in Napa Valley that piques their interest, they are captivated by a deer playfully wandering through the nearby woods. Suddenly, their tranquil moment is shattered when a man with a rifle storms past them and ruthlessly shoots the deer.
After moving into their new home in Napa Valley, Scott and Annie quickly realize they are not alone. The previous owner, Charlie Peck, becomes fixated on observing their every move. Despite Scott’s irritation, Annie feels compassion for Charlie, who shared that his wife succumbed to cancer and that he plans to relocate to Florida to live with his daughter.
During a dinner occasion with their friends, Mike and his wife, Mike steps outside for a smoke and gets an unsettling feeling of being watched. After he carelessly discards his cigarette, he is alarmed to discover a burn mark on the seat of his luxury car the following morning—something that wasn’t there before.
Charlie's frequent, uninvited appearances, where he mows the lawn and chastises workers installing a security system, raise Scott’s suspicions. Mike insists that the couple is being monitored, but both Scott and Annie remain skeptical. To prove his point, Mike convinces Scott to investigate behind the house, where they spot an unfamiliar vehicle driving away quickly.
The tension between Scott and Annie escalates when Annie learns that Scott had a brief affair with a client before they married. While out at a bar, a client illicitly kisses Scott, leading him to realize that Annie’s concerns are justified. When he returns home, an argument ensues, but they eventually reconcile after a startling noise awakens them at night, leading to an intimate moment, entirely unaware that Charlie is lurking nearby.
A neighbor reveals the tragic backstory of Charlie’s wife Ellen, who took her own life using one of Charlie’s shotguns. Concerned for their safety, Scott asks Mike to conduct further inquiries about him. Yet Charlie’s fixation on Annie deepens as he begins to show up while Scott is away. One day, while jogging, Scott is suddenly struck by a truck—driven by Charlie himself.
In the hospital, Scott calls Mike, who rushes to visit him. Scott tells Mike about Charlie’s troubled past, mentioning that he once lived with his wife and daughter in deep financial trouble, forcing him to sell the house. When Charlie unexpectedly arrives at their home, Annie, oblivious to the danger, invites him inside. Mike goes to check on her and confronts Charlie, who chillingly informs him that he believes he can reclaim everything he lost—which includes getting rid of Scott.
In a terrifying turn of events, Mike is brutally murdered by Charlie wielding an axe. Seeking answers, Scott tries to reach out to Cassidy, Charlie’s daughter, but she hangs up when Scott mentions the home. Later, Cassidy calls back, revealing that her father killed her mother after she threatened to leave him. She now lives in hiding, determined to protect herself from Charlie.
Annie uncovers a chilling underground cellar linked to their home, which Charlie has been using as a hideout and where he has unceremoniously stored Mike’s body. In a climactic confrontation, Scott returns home to find Charlie attempting to assault Annie. They manage to fight him off and seize his gun after striking him with a baseball bat.
In a tense moment, Scott urges Annie, who is ready to call 911, saying, >"Make the call, just make the call." Annie hastily informs the police, "My husband has just shot an intruder," while Charlie screams, "You don’t deserve Foxglove!" Ending with a grim statement, Scott tells Charlie, "Go to hell," as he fires the gun, and the screen fades to darkness.
