Posing as a fugitive from justice, frontier undercover agent John Deakin (Charles Bronson) boards a train to go after a ruthless gang of outlaws. Ingredients essential to the action include an anti-military conspiracy involving gunrunners and Indians, a phony epidemic, and a down-and-dirty traintop fight between Deakin and Carlos (boxer-turned-actor Archie Moore). Breakheart Pass was adapted for the screen by Alistair MacLean from his own novel.
~ Hal Erickson, All Movie Guide