Spencer, Sally. DCI Monika Paniatowski mystery.

"On the day of her official retirement from the Force, DCI Monika Paniatowski looks at the two men and one woman who are no longer her team and thinks: Whatever the future holds, I will always be proud of you. She raises a toast. And just like that, her career as a homicide detective is over. Then, fifteen years later, Monika's former sergeant, Kate Meadows, makes a terrible mistake. Monika doesn't hesitate when Kate turns to her for help. She owes her, and she can hardly let her old friend go down for a crime she didn't commit. But as Monika gets deeper into the investigation, she's forced to ask herself the unthinkable: is Kate really innocent, or is she helping her old friend get away with murder?" --