Arthur remained at the rancho all that day, sitting down at the same, table, and eating his dinner with the boys he was about to betray into the hands of the robbers; and, when he went home that night, he had asked, and received, permission to accompany them to the mountains. Their consent had been given reluctantly, and with very bad grace; but they could see no way to get around it. Arthur was a boy with whom they did not care to associate; but he had done them no injury, and they could not bring themselves to refuse his request. "They will start early Monday morning," soliloquized Arthur, as he rode homeward, "and will take the road that leads to Captain Porter's. This is Friday. I shall send word by Joaquin to Pierre to-night, and he will have plenty of time to make all his arrangements." Arthur spent the next day with the boys at Mr. Winters's rancho, and, when he rode over on Monday morning, he brought with him a supply of provisions, which were stowed away in the pack-saddle with the rest. Frank and his friends had been waiting for him, and now that they were all ready, they mounted their horses and rode off--Archie leading an extra horse, which carried the pack-saddle. As they galloped through the Rancheros' quarters, Dick appeared at the door of his cabin, and shouted after them words, which, taken in connection with the events that were about to transpire, seemed like prophecy. "You'll be wishin' fur me an' Bob, to get you out of the hands of that ar' greaser, afore you're two days older," yelled Dick. "You don't suppose that we four fellows will let one man capture us, do you?" shouted Archie, in reply. "If we do get into trouble, and you find it out, you'll come to our rescue, won't you?" "Sartin. Now, don't be keerless, like you allers are." The boys kept their horses in a rapid gallop until they reached the bridle-path in the mountains, and then Archie went ahead with the pack-horse, and the others followed in single file. They rode along singing and shouting, and little dreaming of the danger that was so near, until they arrived in sight of the spring, near which Frank had his last encounter with the robber. He soon found that he was to have another adventure there; for, as he and his companions rode toward the spring, they were startled by a shrill whistle, which echoed among the mountains, and was answered on all sides of them; and, before they had recovered from their surprise, Pierre Costello appeared in the path, as suddenly as though he had dropped from the clouds, and came toward them, holding a pistol in each hand. "Halt!" shouted the robber. The boys looked about them, as if seeking some avenue of escape, and then they saw that Pierre was not alone. Every thicket, toward which they turned their eyes, bristled with weapons, and a dozen revolvers were leveled straight at their heads. It was useless to think of flight. CHAPTER XIII. PIERRE AND HIS BAND.