Colt Clemmons is an agent in a specialized division within the Bureau of Investigation-one that hunts down not just mobsters, but also monsters.

For reasons that are kept top secret, Colt is the only person who can resist a siren's voice. But he's never had a chance to test this ability. The last siren left in the world mysteriously disappeared years ago.

Then one night, with a single word, she reveals herself. It seems too good to be true.

And it is. Because nothing about this siren-her past, her powers, or her purpose-is what it seems …