Bones (Alex Delaware #23) by Jonathan Kellerman

The anonymous caller has an ominous tone and an unnerving message about something “real dead . . . buried in your marsh.” The eco-volunteer on the other end of the phone thinks it’s a prank, but when a young woman’s body turns up in L.A.’s Bird Marsh preserve no one’s laughing.

And when the bones of more victims surface, homicide detective Milo Sturgis realizes the city’s under siege to an insidious killer. Milo’s first move: calling in psychologist Alex Delaware.

The murdered women are prostitutes–except the most recent victim; a brilliant young musician from the East Coast, employed by a wealthy family to tutor a musical prodigy, Selena Bass seems out of place in the marsh’s grim tableau.