A hauntingly beautiful pre-sunrise dawn assaults Frank Dole's senses as he sets out on an early morning surfcasting ritual at a remote shoreline near his summer home. Tiring of the repetitive casting out and reeling in, he wanders aimlessly along the shore and is soon confronted by a mirage both real and alive — a mysterious young woman stretched out on a green towel near the dunes. 

Despite confusion and hesitation, he screws up enough courage to approach and engage her in conversation. Awakening later to an empty beach with no hint of the woman except for her green towel, he proceeds home completely stymied as to who or what she was and why he had fallen asleep. 

Meanwhile, Elizabeth Geary and daughter Merritt have arrived on the island to participate in the reopening of a long abandoned rural church built far out on the moors 50 years earlier by Elizabeth's eccentric grandfather, Matthew Fox. What follows is a virtual treasure hunt, replete with impossible apparitions, obscure clues, surprising discoveries, and a cast of local villagers, each holding ill-fitting pieces of a growing puzzle of the chapel's existence and the mystery girl. 

Frank desperately tries to reconcile subsequent appearances and disappearances of his enigmatic female phantom, all somehow connected to the derelict chapel. Flashbacks to a century earlier reveal the story of Matthew Fox's deep devotion to his beautiful young lover, Jennifer Lydia, their subsequent marriage, her tragic death in childbirth, his 20-year disappearance into the world and later return, and his obsession with designing and building the chapel. 

In the process, the past and present merge into a perplexing amalgam of reality and fiction, resulting in unearthed answers leading to further buried questions. The slow, relentless buildup and arrival of a devastating nor'easter storm brings a surprising resolution to the mystery surrounding the chapel and its builder, as well as the cataclysmic end to the chapel itself.