Cornwall, 1845. Shilly has always felt a connection to happenings that are not of this world, a talent that has proved invaluable when investigating dark deeds with master of disguise, Anna Drake. The women opened a detective agency with help from their newest member and investor, Mathilda, but six long months have passed without a single case to solve and tensions are growing.

It is almost a relief when a man is found dead along the Morwenstow coast and the agency is sought out to investigate. There are suspicions that wreckers plague the coast, luring ships to their ruin with false lights - though nothing has ever been proved. Yet with the local talk of sirens calling victims to the sea to meet their end, could something other-worldly be responsible for the man's death?