It was at Fort Advance, one of the smaller frontier posts on the Indian border, just about the hour of sunset. Buffalo Bill and Colonel Carr, the commandant of the fort, were chatting together when suddenly Buffalo Bill raised his hands and pointed across the plains.A horseman could be seen in the distance, and he was approaching at a furious gallop.Buffalo Bill scanned the figure for a moment in silence."It is Hugh Hardin, the oldest of my scouts," he said, "and I am willing to bet a few cigars that he brings news of a fresh Indian uprising."It was, indeed, Hugh Hardin, and a moment later he had pulled up his steed before Buffalo Bill and Colonel Carr, and, after saluting his superior officers, was making his report.It was to the effect that the Indians to the number of several thousands were on the warpath, under command of Death Face and several other of their chiefs."I scouted near their camp," said Hugh Hardin, "and I know that there is at least one white man in their number. I saw him. He is Eagle, a well-known outlaw. He was formerly chief of the band known as the Renegade Red Riders, which you broke up, Buffalo Bill, not long ago.""What! Eagle, the outlaw chief!" exclaimed the colonel. "I thought you killed him, Cody?""I followed him and drove him off a precipice into Rapid River-man and horse," said Cody; "but it looks as if he had escaped by swimming, and joined the redskins, now that his own band is wiped out. Are you sure that he is with the Indians?""Perfectly," said Hugh Hardin."That man must be captured at all hazards," said the colonel. "I shall immediately order out a troop of cavalry, as well as a battery of infantry, and send them on to oppose the Indians."An hour later the detachment of cavalry and artillery, under command of Lieutenant Worth, one of the most popular young officers in the post, was starting for Rapid River.Two other commands of artillery and cavalry were dispatched immediately afterward.Buffalo Bill headed the column, of course, and when, early the next day, after a hard night ride, they were within a few miles of the river, he advised the lieutenant to call a halt."I will go forward myself on a scout," he said, "before the Indians discover that there is a body of soldiers in the vicinity.""I suggest that you take one of the men in my troop, Sergeant Fallon, as an assistant. He has lived with the Indians for years, and can disguise himself perfectly as one, and speak the language well. Besides, they say that he has powerful friends among the Sioux chiefs. He can enter the camp in disguise, perhaps."Sergeant Fallon, a tall, lean, dark-faced man, stepped forward at the command of Lieutenant Worth, and, after a few words with Buffalo Bill, went off to disguise himself as an Indian, a complete disguise having been brought along with the artillery equipments by command of Lieutenant Worth."He is a mysterious man, evidently well educated," said the lieutenant to Buffalo Bill, "and no one knows why he entered the army, as he is reputed to be very wealthy. He has good cause to wish to be revenged on Eagle, the outlaw chief. Eagle captured his daughter, Lucille Fallon, when she was on her way West, to hold her for ransom, and it was you yourself who rescued her when you wiped out Eagle's band."