2 in the hat

the long version

"Memories of the infamous Blood Bath Killer still loom large, especially for homicide detective Angel Alves, who helped bring down the multiple murderer whose rampage shocked the city. So when a pair of students turn up bizarrely slain, Alves fears that another serial killer is stalking Boston. A fear that becomes fact when Alves's ex-partner, Wayne Mooney, recognizes the murders as the work of the Prom Night Killer, whose unsolved crimes have haunted Mooney for a decade. Now, with hands-on assistant DA Conrad Darget backing them, Alves and Mooney set out to stop grim history from repeating itself. But matching wits with a twisted mind is a dangerous game. Especially when there are no rules, and your allies really may be your enemies."--From publisher description.