Simon and Robyn Callum, portrayed by Jason Bateman and Rebecca Hall, are a couple trying to heal after facing a heartbreaking miscarriage. In search of a fresh start, they relocate from Chicago to California, settling into a charming home closely associated with Simon's past.
Their journey takes a turn when a man named Gordo, played by Joel Edgerton, approaches Simon at a furniture store, claiming to be an old high school acquaintance. Initially unrecognized, Gordo's arrival marks the beginning of a strange and escalating connection between him and the Callums. As an apparent gesture of goodwill, Gordo introduces himself and later brings a bottle of wine as a housewarming gift, further entwining himself into their lives.
Robyn’s hospitality leads her to invite Gordo in while Simon is at work, showcasing their home. It’s during this visit that Gordo references Simon's past campaign for class president, eliciting uncomfortable memories as he drunkenly remarks, >"Simon Says..." about the privileges Simon enjoys in his life. Simon’s discomfort grows as Gordo’s presence becomes increasingly intrusive. In a moment of paranoia and hostility, Simon even scribbles “Weirdo” next to Gordo’s name on their fridge, indicating his profound disapproval of Gordo's visits.
However, Gordo’s behavior continues to cross barriers, marking his territory by leaving gifts, such as koi fish for the pond, and meddling with their cable service. His unexpected dinner invitation only serves to highlight Simon's growing unease. The couple's dinner at Gordo’s home leads to awkward revelations, with Simon whispering derogatory remarks about Gordo’s intentions towards Robyn. As tensions between Simon and Gordo escalate, Simon ultimately demands that Gordo stay away.
Robyn, feeling increasingly unsettled by Gordo’s lurking presence, discovers her koi fish dead and their dog missing, heightening her fears. After an unsettling encounter with Gordo at his residence, the police reveal their prior knowledge of him, painting a disturbing picture of Gordo’s history. Simon’s ambition for a promotion at work contrasts sharply with the chaos unfolding in his personal life, which further clouds their future.
Months later, the couple's lives twist again with Robyn’s unexpected pregnancy. Despite their efforts to live normally, ominous signs persist, including Gordo's continued harassment. His ambiguous intentions become alarming when Robyn learns of the heartbreaking history between Simon and Gordo, where Simon had bullied Gordo mercilessly during their youth. Robyn's investigation into Simon's past unearths disturbing truths about Simon’s actions and Gordo's real character.
The tension culminates at a celebratory dinner for Simon’s job promotion when chaos ensues, leading to a confrontation with a vengeful Danny, Simon's former colleague. As if the situation weren't dire enough, Robyn's labor punctuates the climax, leaving Simon with the burden of emotional trauma.
In a shocking turn of events, Simon discovers Gordo's insidious plans through a twisted gift—a baby bassinet containing incriminating evidence of Gordo’s psychological torment, revealing covert surveillance footage and threatening implications about Robyn’s safety. Feeling cornered, Simon’s descent into despair is palpable as he faces the possibility that Gordo has irrevocably invaded their lives in the worst possible way. Gordo's final revelations imply a deeply twisted revenge against Simon, who ultimately realizes that his past actions have come back to haunt him in unimaginable ways. The harrowing journey leaves Simon contemplating the repercussions of a lifetime of bullying, as Gordo silently watches his world's unraveling, leaving Simon to confront his shattered existence amidst the remnants of their shattered lives.
