Dave Harmon, former lawman, drifted into Miles City. After a casual conversation with well-known rancher, Jeffrey Munro, Munro is attacked by three toughs. When Dave tries to intervene, a fourth man clubs him with a pistol and is about to shoot him when Pete Green, a gambler, kills the attacker.
Green wants no thanks from Dave, but he does tell him that now he owes the gambler a life. Munro persuades the town council to appoint Dave as principal marshal. Pete Green urges Dave to take the job.
It is uncertain how anything will play out, and Dave’s future unfolds in a totally unpredictable, even dangerous way, one in which it becomes exceedingly difficult for Dave to distinguish between foe and friend.