With his dying breath, Rebecca Susan Bennett's father had sworn her to rescue her twin sister Amy -- an Indian captive -- or kill her! It was an oath which would lead Rebecca into the wilds of Montana Territory in the aftermath of the Custer massacre, scouring the high plains on a search that seemed futile, at best, a journey fraught with danger and plagued by enemies -- not the least of them her inner turmoil at having promised in the first place. Rebecca might find Amy -- but if it came to that -- could she really kill her own sister? Her twin?