The Merlin Pool by Monte Merrick

While Tom Jessup is touring Yellowstone National Park with his dog, Buster, a member of a tour group is murdered by being shoved into one of the volcanic pools. Though Tom doesn’t want to get involved, he soon finds himself up to his neck in clues and secrets. When more murders happen, Tom knows he must find the killer or he - or his beloved dog – could be the next victim.