Treachery In Death: 32 by J. D. Robb
Detective Eve Dallas and her partner, Peabody, are following up on a senseless crime - an elderly grocery owner killed by three stoned punks for nothing more than kicks and snacks. This is Peabody's first case as primary detective - good thing she learned from the master. But Peabody soon stumbles upon a trickier situation. After a hard workout, she's all alone in the locker room when the gym door clatters open - and while hiding inside a shower stall trying not to make a sound, she overhears two fellow officers, Garnet and Oberman, arguing. It doesn't take long to realize they're both crooked - guilty not just of corruption but murder. Now Peabody, Eve, and her husband Roarke are trying to get the hard evidence they need to bring the dirty cops down - knowing all the while that the two are willing to kill to keep their secret.