Vic (Ben Affleck) and Melinda Van Allen (Ana de Armas) are a couple navigating the complex waters of a troubled marriage, living in the quaint town of Little Wesley, Louisiana, along with their daughter, Trixie (Grace Jenkins). Vic, a retired robotics engineer who once thrived in the competitive tech industry, found fortune in developing the critical guidance chips utilized in combat drones. However, despite their outward appearances, their relationship is far from ideal. Their bond hinges precariously on a unique arrangement: Melinda is permitted to take lovers without the complications of divorce, as long as she remains physically present for her family. This unconventional "open marriage" is no secret among their social circle, inevitably leading to rising tensions as Vic grapples with his simmering jealousy over Melinda’s escalating list of affairs, while Melinda laments Vic's flagging enthusiasm and emotional distance.
Melinda is undeniably attractive, and she constantly teases Vic by placing him in situations that undermine his comfort. One particular incident involves Melinda asking Vic to choose a daring dress for one of her dates. Vic feels the weight of knowing he can only gaze without being able to touch Melinda, adding to his internal strife. Their babysitter, Chelsea (Juliet Brett), often navigates the chaotic moments in their home, which serve as a backdrop to their tumultuous existence together. Intriguingly, Vic harbors an unusual hobby: he maintains a snail farm in his garage, a passion that provides him with a sense of solace amidst the chaos of family life. In contrast, Melinda struggles with motherhood, feeling more exasperated by Trixie's demands than affectionate towards her daughter, leading Trixie to form a closer bond with Vic.
The situation escalates when Melinda's lover, musician Joel Dash (Brendan Miller), is invited to a party attended by Vic. It is there that Vic witnesses Melinda sharing an intimate kiss with Joel by the swimming pool, igniting a toxic mix of anger and envy within him. Alone with Joel, Vic ominously confides that he is culpable in the disappearance of Melinda’s last boyfriend, Martin McRae, who vanished under suspicious circumstances. Despite Vic’s daunting revelation about supposedly killing Martin with a hammer, Joel chooses to hastily exit the gathering, visibly shaken.
As the narrative unfolds, Joel moves to Santa Fe, prompting Melinda to conspire with Vic to lure him back for a dinner and an apology. Nonetheless, even amidst the apology, Vic reiterates his grim confession about Martin’s fate. Complications arise when a news report announces that Martin’s body has surfaced, leading to the arrest of a prime suspect, sending tremors through their close-knit group of friends, particularly alarming noir writer Don Wilson (Tracy Letts) who begins piecing together the uncomfortable truths hidden beneath the surface.
Vic’s unexpected connection with Don’s wife, Kelly Wilson (Kristen Connolly), at a social function raises eyebrows among their friends, with all noting a spark between them that Vic hadn’t shown before. Meanwhile, Melinda attempts to rekindle intimacy with Vic, culminating in a spontaneous moment of passion on the very night Vic shares an embrace with Kelly—a juxtaposition of their intertwined fates.
The plot thickens when Melinda’s relationship with piano teacher Charlie De Lisle (Jacob Elordi) puts Vic on edge. His growing jealousy escalates when Melinda invites Charlie to an extravagant pool party at the home of Vic's friend, Jonas Fernandez (Dash Mihok). When everyone is called indoors to escape a sudden downpour, they are met with the shocking sight of Charlie lifeless in the pool, apparently having drowned. Accusations swiftly fly when Melinda insinuates Vic may be involved in Charlie's death, heightening suspicions among their acquaintances, including Don, who grows wary of Vic's behavior.
In a menacing twist, Vic, now motivated by jealousy, confronts Charlie and ultimately leads him to a secluded area where he pushes him off a rocky hill to his demise. Transporting Charlie's body later becomes a psychological struggle for Vic. His intent to recover Melinda's lost scarf from a nearby creek serves as a double-edged sword, where Vic finds himself drawn back to the very spot of his latest crime. However, it is not long before Don catches Vic in the act while trying to dispose of Charlie's remains. In a climactic moment, a desperate chase ensues, resulting in an accident that claims Don's life, adding another layer of complexity and guilt to Vic’s already tumultuous existence.
As the story spirals deeper into a web of deceit, Melinda, sensing the increasing pressure, discovers incriminating evidence of Vic's involvement in the suspicious deaths when she finds Charlie’s ID in one of Vic’s snail tanks. She prepares to escape with Trixie, only to have her resolve tested by her daughter's heartfelt plea for her to stay. Melinda's moment of contemplation leads her to destroy Charlie's identity documents—an act that suggests she may be choosing to remain with Vic. Despite their fractured relationship, the pain and attraction they share indicate that the tangled web they have spun binds them together in a way that neither can easily escape.
