Devil Bones by Kathy Reichs

In a house under renovation, a plumber uncovers a cellar no one knew about, and makes a rather grisly discovery a decapitated chicken, animal bones, and cauldrons containing beads, feathers, and other relics of religious ceremonies. In the center of the shrine is the skull of a teenage girl. Meanwhile, on a nearby lakeshore, the headless body of a teenage boy is found by a man walking his dog.