An urgent call for help from their father's old friend, chemist Sam Gentle, has Frank and Joe Hardy heading across country to the wild landscape of Arizona. Bit it seems they're already too late:as the eminent chemist is already lying dead at the bottom of Wolf Tooth's Canyon. Their friend's death only makes the brothers more determined to get to the bottom of the mystery, even if it means deciphering cryptic clues left from beyond the grave and tackling unknown enemies with nothing but murder on their minds.