The Siren's Legacy

Sapphire Stone is the only one of her kind, half-siren and half-mermaid. Yes, mermaids and sirens are totally different supernatural beings. But they have one similarity between them, they both possess hypnotic voices. What's makes her life more interesting is that, she works as a detective in the Criminal Investigation Division (CID) under the Port Of Seattle Police Department (POPSD). But that's just a cover for her real job. She is an Undercover Agent working for The Paranormal Bureau Investigation Of Supernatural Crimes. Life was going normal untill a series of murder starts happening under the deep waters of Lake Union. What happens when Detective Sapphire finds out that are not ordinary but have a supernatural edge to it?