Bad Omen

Lindy Lindemann always thought she would like to work in a library. Instead, she's a police dispatcher using her abilities as a precognizant to help the people and feed information to the police when she can. One by one, the high-ranking witches in the city start being picked off, and after every murder, a man identifying himself only as A calls to let her know it's him.
With the police quickly running out of leads, Lindy is brought in to work with the lead detective, Dick Hobard. Lindy discovers that these killings are connected to the murder of a family that happened over ten years ago. The only problem? The person that Lindy suspects is Staff Sergeant Siobhan Cockburn, the one who brought her into this in the first place.
Now, Lindy not only has to stop A from killing anyone else, but also prove that Cockburn isn't what she appears before A adds them both to his list.