Flint is riding ahead of the train with Bill Hawkes when they hear gunshots. Heading in the direction the shots have come from they soon find the evidence of an Indian raid on a small camp site. While Flint is looking around the site, trying to get a clue as to who the victims and assailants were, Bill finds a spent bullet casing. It looks to the two men as if the Indians who attacked the camp have got hold of the newest type of army rifle. Flint sets out to find out if he can track down the gunrunner. He doesn't have to go far before he can see the smoke from a campfire. When he finds the camp his suspicions are aroused by the amount of smoke the campfire is stoked up to make, and during daylight at that; one man, one woman, one wagon, but with a team of horses strong enough to pull a heavier load than the blankets the man claims to be carrying to trade with Indians.In spite of hostility from the man (known as Doc) Flint invites himeself into the camp. When he thinks Doc and the woman (Dora Gray) are asleep he goes to the wagon where his suspicions are proved right. The wagon is full of boxes of the new army rifle. Doc was obviously camped here, waiting for the Indians and that was why his fire was built to smoke. Flint is determined to take the wagon and Doc and Dora to Fort Spear, the nearest large fort where they can stand trial for gun running. Doc, however, manages to escape on Flint's horse leaving him with Dora. She gets on his nerves so much that he changes his plans and instead goes to the nearest army camp, the Old Grace Cavalry Post. Dora is even more reluctant to go there than to Fort Spear but won't tell Flint why, just that "you'll be sorry." When they reach the post her words come true- it is Flint who ends up behind bars, not Dora.