Nellie Sanders persuades her uncle, a renowned botanist, to allow her to join an expedition to the Sawtooth Valley in Idaho Territory in 1872. Using an assumed name, infamous shootist Malachi Breedlove contracts to lead the botanical expedition into the wilderness.

A crazy old woman steals Nellie, believing her a dead daughter returned to life. As leader of the expedition, Malachi is forced to send others to seek the woman he now realizes he loves. Nellie finally convinces the old woman to take her back, claiming she will die without Malachi.

No sooner are Nellie and Malachi reunited than disaster strikes the expedition. Now the lovers must face the dangers of the wilderness must, conquer old weaknesses and discover new strengths. As the summer ends, Nellie faces a choice between academic acclaim and love, while Malachi wonders whether he can hang up his guns and survive. Can they find a compromise that lets them both realize their dreams?