A woman studying a crime of the past finds her own life becoming a morass of suspicion and deceit in this drama based on the novel by Anita Shreve. Jean Janes (Catherine McCormack) is a photographer working on a project that would document surviving evidence of a multiple murder that occurred a hundred years ago -- when a man named Louis Wagner (Ciaran Hinds) brutally killed two immigrant women from Norway with an axe, only to discover a third, Maren Hontvedt (Sarah Polley), witnessed the mayhem and survived to identify him in court. Jean travels to the small New Hampshire coastal town where the killings occurred with her husband Thomas (Sean Penn), an award-winning poet; his brother Rich (Josh Lucas); and Rich's girlfriend Adaline (Elizabeth Hurley). As Jean digs deeper into the troubling facts of the long-ago murder, as well as the tangential details of Maren Honvedt's unhappy marriage to John Hontvedt (Ulrich Thomsen) and her incestuous affair with her brother Evan (Anders W. Berthelsen), Jean begins to believe that she has a crisis of her own to contend with: she is convinced Thomas is having an affair with Adaline. The Weight of Water also features Katrin Cartlidge as Maren's sister Karen and Vinessa Shaw as her sister-in-law Anethe.