From The TV IV
Its winter and the Sioux are at war and the Wyoming Territory has become their battleground. Slim Sherman and Jess Harper have to close up Sherman Ranch and Relay Station, sending Jonesy and Andy Sherman to Laramie and to safety. Slim and Jess volunteer with Army, Jess ends up as guide for Custer and Slim assigned to guide a mule train carrying dynamite up to a critical mountain pass. The pass must be blown up to prevent the Cheyenne from joining the Sioux and trapping Custer's forces between them. It's up to Slim, aided by a beautiful woman, to win the battle against the elements, against the Cheyenne and against the betrayal of white trappers to make sure that the mission succeeds.