The Bristol Sea divides Cornwall and Wales—and sings an enticing tale to Sienna Rothesay, a British born, American raised photographer. Since childhood, she’s fought the temptation of its siren song, with only broken bones and scars to show for giving into the whispers of the waves. Scorned by her family for her injuries, she confides in her adoring grandfather—the lone family member who hears the music with Sienna. When Ioan Morgannwg, an enigmatic neighbor from her British days calls her home to help with her failing grandfather, Sienna is faced with an old myth that hints at a nefarious secret, linking her ancestors with Ioan’s. As her grandfather's mind deteriorates, he obsesses over the siren song. Time slips away as Sienna rushes to solve the puzzle before her grandfather dies, burying the secrets with him. Family against family, father against son—a gripping tale of betrayal is revealed to Sienna, forcing her to question everything she knows, about herself, about her family and especially about love.