Shortly after her arrival at Brooklyn North Homicide, Detective Kim Brady is assigned a seven-month-old rape and murder of a 14-year-old girl. While the initial investigation focused on a teen suspect, DNA evidence, as well as the killer's signature, establishes that the killer was also responsible for several older crimes, including the 1963 case Kim's grandfather was working when he was killed. She is chasing a killer who's been on the loose for fifty-five years.

Kim's investigation takes place against the backdrop of a special mayoral election pitting a "law and order" state senator against the "defunder" acting mayor. A protest group is accusing the police of letting the case go cold because the victim is a Latina and stoking protests that result in arson and the killing of a firefighter. While Kim awaits the result of DNA analysis, her headquarters receives two bomb threats and the killer strikes again... and again... and again.