The Drowning House by Cherie Priest
On a stormy night, off the coast of Washington, an elderly woman is terrified to death when she sees a house washed up on the beach, one she recognizes from her nightmares. When Melissa tries to contact the woman's grandson, Simon, a police officer answers his phone, revealing that Simon is missing. Desperate to find him, Melissa and Leo, once close childhood friends but now estranged, reunite on the island to uncover dangerous secrets that could hold the key to Simon's fate.