Rachel White, portrayed by Ginnifer Goodwin, is a single attorney navigating her career in a bustling New York law firm. On her 30th birthday, after indulging in too many drinks, Rachel finds herself sharing a cab with Dex, played by Colin Egglesfield, where she opens up about her long-held crush on him from their law school days. However, there’s a catch — Dex is engaged to Rachel's best friend, Darcy, who is brought to life by Kate Hudson. The morning after their playful night together is disrupted by phone calls from Darcy, fueling an awkward situation that neither Rachel nor Dex can fully address at first.
Initially, Rachel believes their intimate encounter is merely a fleeting one-night stand, but it soon blossoms into a heartfelt affair after Dex confesses his love for her. This ignites a complex web of lies, as Rachel and Dex fabricate stories to conceal their romance from Darcy and others in their circle. Rachel spins elaborate tales of sexual exploits with Ethan, played by John Krasinski, and Marcus, to obscure the reality of her relationship with Dex.
As the plot unfolds, we learn that Rachel’s infatuation with Dex dates back to their law school days. Although she revealed her feelings to Darcy, it was Darcy who ultimately captured Dex's heart instead, casting a shadow over Rachel's aspirations. Meanwhile, Darcy continually tries to set Rachel up with Marcus, yet Rachel finds herself disgusted by him.
Ethan, a childhood friend of both women, becomes privy to the secret between Rachel and Dex, which he struggles to keep under wraps as he watches Rachel deceive those she truly cares for. Complicating matters further, Dex's mother is battling depression, finding solace only in the planning of Dex and Darcy's wedding. Dex feels torn as he chooses to spend the Fourth of July weekend in the city with Rachel rather than with his family, causing his father to warn him to prioritize what is morally right.
As the wedding approaches, the tension mounts, and Rachel becomes increasingly desperate. During a beach trip, Ethan nearly exposes their secret, only to be painfully rebuffed by Rachel. Their relationship reaches a critical point when Rachel confronts Dex at a bar, imploring him to cancel the wedding, but he cannot bring himself to make that leap. Ethan's move to London becomes a turning point, where he admits his love for Rachel and her obliviousness to the affection surrounding her.
Upon her return to New York, Rachel is overjoyed to discover that Dex has called off his engagement to Darcy, but that joy swiftly dissipates when Darcy arrives at her apartment, revealing her infidelity with Marcus and her unexpected pregnancy. After a heated exchange that exposes their mutual betrayals, Darcy storms out, leaving Rachel to navigate the fallout with Dex.
Two months later, a chance encounter in the city sees Rachel and Darcy crossing paths. While both claim to have moved on, unspoken tensions linger as they each bear the scars of their shared history. In a powerful moment of underlying emotion, they exchange smiles before Rachel finds Dex again, and they walk together hand in hand down the street.
In an intriguing twist, the film closes with a cryptic scene during the credits, suggesting the potential continuation of their story as Darcy seeks out Ethan in London, leaving viewers pondering what lies ahead for this tangled trio.
