Promises in Death (In Death, 28)

Amaryllis Coltraine may have recently transferred to the New York City police force from Atlanta, but she's been a cop long enough to know how to defend herself against an assailant. When she's taken down just steps away from her apartment, killed with her own weapon, for Eve Dallas the victim isn't just "one of us."
Dallas's friend Chief Medical Examiner Morris and Coltraine had started a serious relationship, and from all accounts the two were headed for a happy future together. But someone has put an end to all that. After breaking the news to Morris, Eve starts questioning everyone from Coltraine's squad, informants, and neighbors, while Eve's husband, Roarke, digs into computer data on Coltraine's life back in Atlanta. To their shock, they discover a connection between this case and their own painful, shadowy pasts.
The truth will need to be uncovered one layer at a time, starting with the box that arrives at Cop Central addressed to Eve containing Coltraine's guns, badge, and a note from her killer: "You can have them back. Maybe someday soon, I'll be sending yours to somebody else."
But Eve Dallas doesn't take too kindly to personal threats, and she is going to break this case, whatever it takes. And that's a promise.