Enrique Armijo, archaeologist, and in his own mind, the world's authority on the Folsom Man culture, is spying on a ritual performed by the so-called Skin People in the crater of Capulin Mountain, an extinct volcano in northern New Mexico. He doesn't expect to be murdered. He certainly doesn't expect the weapon to be a prehistoric atl-atl. Back in Crawford County, Texas, Sheriff Charles Matthews doesn't expect a call from his deputy, Raul Trujillo, about the archaeologist's murder and the bizarre weapon used.

He certainly doesn't expect to hear that the atl-atl has been found in his deputy's hotel room and that Raul is charged with murder. Knowing that no matter what the evidence says, Raul didn't murder anyone, Charles leaves his badge behind in Texas and steps into New Mexican Sheriff Kit Lindman's territory to prove his deputy and friend innocent.