The last crossing - Guy Vanderhaeghe

Charles and Addington Gaunt must find their free-spirited brother, Simon, who has gone missing in the wilds of the American West. They enlist the services of a guide to lead them on their journey across a harsh and unknown landscape. This is the enigmatic Jerry Potts, half Blackfoot, half Scottish, who suffers his own painful past.
They are joined by Lucy Stoveall, a woman filled with rage and sorrow over the loss of her young sister Madge who was brutally murdered. She is on a vengeful mission to track down and kill the murderous Kelso brothers. The group is joined by a jumble of other characters en route, each of whom are forced to confront their own demons.
But at the novel's centre is a love story. Vanderhaeghe glides effortlessly through the patois and frontier talk, faultlessly switching from cultured English characters to American roughnecks to Scots-Canadians, and the natural prairie landscape is evoked brilliantly.