Longarm and the Grand Canyon murders

"Sink or swim? Judge Quinn and his lovely young wife have disappeared without a trace. The couple was last seen taking a boat ride on the Colorado River--and now three river guides have been found with their throats slit. To get to the bottom of the mystery, Longarm needs to get to the bottom of the Grand Canyon. With a Dutch beauty named Heidi at his side, Deputy U.S. Marshal Custis Long fights off back-shooting bushwackers just to reach the rim...