City of the Dead by Jonathon Kellerman

 Psychologist Alex Delaware and his police lieutenant friend,  Milo Sturgis, get called to a bizarre crime scene. A naked man was hit by a moving van in the early hours of the morning. But it doesn't look like that's what actually killed him. And when they explore further, they find a dead woman in the house he had come from. She was a woman who had gotten in trouble with the law for masquerading as a psychologist and had rebranded herself as a relationship expert. But who was the intended victim and who was just in the wrong place at the wrong time?

It's a good but twisty case with a surprise ending. I do love the friendship between Alex and Milo and eagerly await their next case.