Based on the book by Anita Shreve.
An intense and sexually-charged drama of repression, love, and loss, in the past and in the present, THE WEIGHT OF WATER tells the story of a contemporary woman whose obsession with a notorious unsolved crime from the 1800s leads her to confront devastating truths in her own life. Jean (Catherine McCormack), a photographer working on a magazine story about the case, and her husband, Thomas (Sean Penn), a troubled poet, view their trip to New Hampshire's picturesque Isles of Shoals, the scene of the crime, as a respite from their ongoing marital problems. But as Jean immerses herself in the details of the murders an outburst of passion that resulted in the deaths of two women she enters precarious emotional territory.
On her brother-in-law Rich's (Josh Lucas) sailboat, Jean's suspicion that Thomas is having an affair with Adaline (Elizabeth Hurley), Rich's alluring new girlfriend, escalates into jealousy and distrust and sets into motion a series of events with tragic consequences. Blinded by her fear that her husband is being unfaithful, Jean fails to see the more significant flaws in their relationship. Ruled by unpredictable and unreasonable emotions, she is the architect of her own unhappiness. Jean's situation is further complicated by the fact that she finds herself attracted to Rich.
Interwoven with this present-day psychological drama is the period story of the double-murders. In 1873, Anethe (Vinessa Shaw) and Karen (Katrin Cartlidge), both young Norwegian immigrants, were brutally murdered. A third woman, Maren Hontvedt (Sarah Polley), a young immigrant trapped in a loveless marriage and obsessed with a clandestine love affair from her past, survived. Louis Wagner (Ciaran Hinds), a former border at the Hontvedt household, was tried, convicted, and executed for the murders. But Jean discovers documents that suggest he was innocent.
Jean's two obsessions -- the murders and her deteriorating marriage -- collide in explosive and unexpected ways. During a sudden storm at sea, one that mirrors the tempestuous emotions of the four people on the boat, Jean's explosive feelings of jealousy, frustration, and rage illuminate the terrible truth about the killer and the killings. She has a flash of insight, finally understanding what really happened the night of the murders.