Detective N.K. Boswell of the Rocky Mountain Detective Agency is on the trail of Kane Kelly who shot a boy dead in Laramie. Finding the man is easy. He's supervising a railroad crew in Iowa. Bringing the man to justice in Wyoming will be difficult. Four hundred miles of open prairie and flooded rivers aren't the only obstacles however. Kelly's brother Sligo and his gang of toughs are determined to stop Boswell at all costs, but Boswell lays a cunning trap using his prisoner for the bait. If it works, Boswell will arrest Sligo as well...if it works.