In 1850s Oregon, Eli and Charlie Sisters are notorious assassin brothers employed by a wealthy magnate known as the Commodore. Tasked with killing Hermann Kermit Warm, a chemist who has allegedly stolen a formula valuable to the gold mining industry, the brothers pursue their target through the dangerous and lawless American frontier. While Charlie revels in the chaos of their profession, Eli yearns for a more peaceful and stable existence, creating an underlying tension between the siblings as they execute missions rife with brutality and bloodshed.

Simultaneously, John Morris, a detective hired by the same employer, has been tracking Warm from town to town, capturing detailed reports of his whereabouts. When Morris finally meets and befriends Warm, he learns of the chemist's noble intentions behind his discovery that promises a revolutionary way of prospecting gold. However, the developing camaraderie between Warm and Morris complicates the mission, ultimately intersecting the paths of the detective and the assassin brothers. As allegiances shift and the harsh realities of their environment test them, each man begins to question the purpose and price of their violent livelihoods.