Derek Charles, a successful asset manager, has just received a promotion and moved into a new home with his wife, Sharon, and their son. The family's idyllic life begins to unravel when Derek hires a temporary worker, Lisa, who is both attractive and efficient. Initially, Derek appreciates Lisa's work ethic, but he becomes increasingly uncomfortable as her admiration for him escalates into a clear obsession. Despite Derek's attempts to maintain a professional distance, Lisa's behavior grows more alarming, crossing the boundaries of a normal workplace relationship and delving into inappropriate and uninvited advances.

Sharon becomes aware of the situation when she visits Derek at his office, leading to tension between the couple. As Lisa's attempts to seduce Derek become more brazen, his efforts to protect his career and marriage intensify. He confronts Lisa, hoping to put an end to her advances, but she is undeterred, her obsession deepening to the point of breaking into the couple's home. The confrontation between Derek's efforts to safeguard his family and Lisa's relentless pursuit sets the stage for a dangerous escalation, threatening not only the peace of Derek's household but also the lives within it.