Frank and Joe take off on a cross-country skiing trip into the Colorado Rockies and soon find themselves facing the greatest challenge of all: a test of survival! They've befriended a conservationist K.D. Becker, a woman dedicated to saving the endangered mountain lion. But K.D.'s been shot -- and now it's her life that hangs in the balance.

The boys discover that K.D.'s mission to create a wildlife preserve has stirred up passions as old as the frontier itself. Ranchers, hunters, and native Americans all want the land -- and K.D. stood in the way. The hunt is on, and the Hardys are hot on the trail of suspect. But the shooter's not about to give in without a fight, and now Frank and Joe have become fair game!