In Southport, Maryland, we meet Susan Morrison (Teri Polo), who has recently divorced her husband Frank (John Travolta), a boat builder struggling to keep his business afloat. With the demand for boats dwindling, Frank is forced to sell his creations for next to nothing, jeopardizing the longevity of his livelihood.
Meanwhile, Susan has found love again with Rick Barnes ([Vince Vaughn]), a younger, affluent man. Their twelve-year-old son, Danny ([Matt O'Leary]), is visibly distressed about his mother's impending marriage. In an attempt to help Danny and Rick bond, Susan asks Frank to take them sailing together.
Rick, who recently hit it big investing in the stock of a pharmaceutical company that developed a groundbreaking blood pressure medication, has now purchased a new resort and desires Frank to craft boats for it. As the family dynamics shift, Danny struggles with acceptance, resorting to petty theft and reckless behavior as he seeks attention and attempts to reunite his parents.
Frank, meanwhile, is dating Diane ([Susan Floyd]), who believes he is still clinging to his past with Susan. The friction escalates when Frank learns that Rick has questionable connections, particularly when a figure named Ray (played by Steve Buscemi) unexpectedly turns up at their wedding, claiming to be an ex-business associate of Rick, worsening tensions all around.
Rick and Susan soon tie the knot, but a shocking twist occurs—Rick's scandalous past resurfaces when Danny witnesses him committing murder. As Danny grapples with the horrifying reality of his mother's new husband being a killer, he takes the drastic step of informing his father and the police, putting everyone in danger.
Despite his initial doubts, Frank conducts an investigation that reveals Rick's true identity as Jack Parnell, a man with a nefarious history. The stakes rise when Jack's attempts to eliminate Frank culminate in a series of tense confrontations. When Jack takes Danny hostage with the intention of fleeing, Frank is forced to confront him in a fierce struggle.
In a climactic moment, Danny plays a crucial role in Jack's downfall, which leads to a fraught yet crucial showdown. As the dust settles, Susan realizes the truth behind Jack's manipulations, and although she suffers a miscarriage during the chaos, she is ultimately united with Frank and Danny.
In the aftermath, the police issue an apology, acknowledging the belated trust in Danny's claims. The reunion of the three emphasizes the resilience of family, even in the face of harrowing adversity.
