Shadow's Edge - Psychic Mysteries Series, #1

Liam Baker can see things. Dead people like to visit him and tell them how they were wronged. Some might call it a gift, other's a curse. But either way this ability makes him useful to Los Angeles homicide detective Kimball Thompson. Some madman is slitting the throats of young male prostitutes and then dumping their bodies in the desert with vague clues of pink feathers and the number five. Usually Liam can talk to the spirits of the dead.
But someone is blocking him. Someone is taunting him. The case is rapidly deteriorating into a violent, psychic pissing contest and Liam can't see far enough ahead to figure out who wins or who dies.