The year is 1825
The story begins with a British aristocrat named John Morgan who finds himself captured by Sioux warriors
At first he's mocked and treated like an animal and then he's dragged to their camp where he is given to work for an old squaw (Judith Anderson).
Before too long the 'grand white gentleman' up with another captive Batise (Jean Gascon) whose family was all massacred five years ago by the Indians acts as translator for Morgan
One day after killing two Shoshone Indians from another tribe and scalping one of them, John gains trust and respect from his captives thus paving the way to be soon a warrior, then a loving husband
The film's centerpiece is the Sun Vow that Morgan must bear to prove his courage to withstand all tests of pain in order to gain the hand of Running Dear (Corinna Tsopei) sister of Chief Yellow Hand (Manu Tupou). As the English nobleman is white, he is considered weak and he'll give up in the moment of truth
There are also other truly memorable moments in the film: how the Indian virgin prepares herself for marriagehow she takes her sweat bath to be pure; and the tragic events when an Indian mother loses and has no other son or man, how she cuts off her forefinger and when winter comes she dies from the freezing cold