Who is the narrator in dead letter?

In the novel "Dead Letter" by James Patterson and Candice Fox, the narrator is Detective Harriet Blue, a seasoned homicide detective based in New York City. She is a complex and determined character who is tasked with investigating a series of grisly murders that bear an eerie connection to the lost letters of an enigmatic criminal known as "The Highwayman." As the story unfolds, Detective Blue delves into the depths of the case, uncovering dark secrets and confronting her own demons along the way.