Deputy U.S. Marshal Spurr Morgan's ticker isn't what it used to be. After Spurr suffers a heart attack on the job, the chief marshal convinces him it's time to step down. But Spurr asks for one last assignment. The chief sends him to bring a prisoner back to Denver from the Medicine Bow Mountains. The mission seems routine for an old hand like Spurr, until he discovers that the criminal in question is his old nemesis, Boomer Drago -- the former lawman turned train robber that Spurr's been trying to run down for years.