A Heart So Wild by Johanna Lindsey

Courtney Harte is certain her missing father is a alive, lost somewhere deep in Indian territory. But she needs a guide to lead her safely through this dangerous, unfamiliar country, someone as wild and unpredictable as the land itself. And that man is the gunslinger they call Chandos.

Courtney fears this enigmatic loner whose dark secrets torture his soul, yet whose eyes, bluer than the frontier sky, enflame the innocent, determined lady with wanton desires. But on the treacherous path they have chosen they have no one to trust but each other--as shared perils to their lives and hearts unleash turbulent, unbridled, passions that only love can tame.