A young boy is riding across the prairie when he sees an Indian woman skinning a buffalo. He is frightened by this because the Comanches have been raiding individual farms around Dodge. He raises the alarm to some men who are drifters on the prairie and then Marshal Dillon encounters them. They all ride out to investigate and find that the indian woman is not part of some war party. Instead, Shona is the Indian wife of a trapper, and she was just out on the prairie getting another fur. The drifters ride off in disgust, but they aren't done causing problems. They hang around Dodge City inflaming mobs to go out and take care of matters with the Comanche themselves, and they are bullying and threatening any Indians who come into Dodge, including half Comanche blacksmith Quint (Burt Reynolds).
And then the cut on Shona's hand gets badly infected and she and her husband must come to Dodge and stay for a few days so that Doc can treat and dress the wound multiple times a day. This infuriates the gang of drifters who have set up camp in Dodge, and in the face of this simmering violence Matt leaves town on business! With nobody deputized to deal with this in his absence! Well, without this badly reasoned turn in the story there would be no plot. OR Matt could have taken what was a well used page back in 19th century law books and even 20th century ones. These drifters had no visible means of support. He could have put them in jail for a few days as vagrants until they cooled off and then made them leave town. But then again we would have no plot.
The one thing that the camera makes a point of having the viewer notice - the menacing smirk on the face of the brother of the ringleader of the violent gang every time he looks at Shona. I have to credit the director for getting just the right look on this guy's face. It's not a smitten look but instead is quite a sinister yet subtle expression.