Carey Kyle Marvin and Ashley Adria Arjona are a married couple who, while driving on the highway, briefly try to share a moment of intimacy before they witness another couple crash beside the road. They pull over to help, finding the husband barely conscious and the wife ejected from her seat. Despite Ashley’s earnest attempts at CPR, the woman dies. The shock reveals painful truths: Ashley confesses she wants a divorce and that she has been unfaithful. Struck by the events, Carey heads to the beach house of his best friend Paul Michael Angelo Covino and his wife Julie Dakota Johnson seeking support, only to learn they are in an open relationship, a revelation that unsettles him.
The following day brings a fresh complication when a man accuses Paul and Julie’s son Russ of stealing his jet ski. With Paul away on business, Carey defends Julie, and the situation escalates into a confrontation that ends with Julie stepping in to calm things down by forcing apologies from the aggrieved party. That night, Carey and Julie grow closer and eventually consummate their bond. When Paul returns, Carey recounts what happened, and Paul’s anger flares into a violent argument within the house, quickly quieted only when Julie intervenes and insists on restraint from all involved.
Later, Carey joins Julie and Russ at a carnival, where jealousy stirs after Brent [O-T Fagbenle], the father of a friend of Russ, flirts with Julie. Julie confronts Carey about the tension, and he admits that the moment meant more to him than he expected. She urges him to move on. Returning home, Carey discovers Ashley sleeping with another man. Ashley presses him to leave, but Carey proposes expanding their arrangement into an open relationship to avoid divorce. Ashley agrees, albeit cautiously, after Carey reveals he has already slept with another woman—but conceals that the encounter was with Julie. Ashley then begins a string of short-term lovers, with Carey tactfully befriending them and even inviting them to stay at the shared home, much to Ashley’s irritation.
Paul arrives to confront Carey, and Ashley eventually learns that the “other woman” was Julie. Julie then encounters Carey at Russ’s school and learns that Paul’s company has folded, their assets are frozen, and they are effectively bankrupt. Carey admits his growing feelings for Julie, which she reciprocates. Paul witnesses Carey and Julie sharing a kiss and persistently questions whether they are really involved, trying to pry out the truth.
After a disciplinary meeting at Russ’s school, Julie accuses Paul of wrongdoing involving loans taken in Russ’s name and confessing to her relationship with Carey. Paul is jailed, and upon his release he agrees to sign divorce papers for Julie. Paul and Ashley, frustrated by Carey's ongoing involvement with Julie and his indifference to her own lovers, briefly consider rekindling something with jealousy in mind but decide against it.
At Russ’s birthday party, Ashley arrives with her lover Matt Nicholas Braun, a mentalist performing for the guests, while Paul brings a woman who bears a striking resemblance to Julie to provoke her. Ashley tries to win Carey back, and he admits he felt jealousy over her lovers and had been keeping company with them to irritate her. Ashley kisses him, but he insists they remain friends. Julie privately confronts Paul, who admits that he too never slept with anyone else during their relationship and admits he opened things up out of insecurity. They reconcile and share a moment of intimacy, which Carey walks in on, sparking a tense confrontation among the four.
The tension finally eases after they extinguish a small fire caused by Russ’s birthday candles. Some time later, Carey and Ashley are together again and have welcomed a baby. Paul and Julie remain apart but keep a sexual relationship. When all four adults are gathered at Paul and Julie’s former beach house—now listed as an Airbnb—Carey and Paul get into a heated exchange with a neighbor over a jet ski dispute, underscoring that their complicated arrangements continue to haunt them even as life moves forward.
