Jack Allen's mind was bitter, as he followed Jim's trail. Why had Jim done this thing? As a sort of dare? No, he knew that was not the answer. Then why? Some fool idea of learning something from a letter? That was it. But the fool must be taught that Uncle Sam's mail is sacred. Jack Allen fought a bitter battle with himself as he rode through those winding hills. He cared more for Jim than for anything else in the world--save the law! He found his outlaw brother's trail easy to follow. No attempt had been made to throw off possible pursuit by a false scent. "He's in a hurry now. He'll try his stuff later. He's sure enough circling back to the gulch," Jack Allen told himself. It was well past noon when the Wyoming sheriff suddenly pulled his horse to a sliding stop and led it into the shelter of some brush. He tied it and then began to crawl between the clumps of sage. He breasted a slight hill. Not twenty yards away he saw Jim sorting the mail from an open mail bag at his feet Jack crouched lower and crawled ten yards nearer, then sprang upright. His gun was in his hand, as he called: "Put 'em up, Jim, or, by Heaven, I'll shoot!" Jim Allen turned his head and stared at his brother, then slowly raised his hands. In one of them was a packet of letters. Jack Allen picked his way through the brush toward Jim. But he was forced to keep his eyes on his brother, and one of his extra-high heels betrayed him. He slipped and nearly fell. During the second when Jack's eyes were off him, Jim's hand moved with incredible swiftness, and the little packet of letters was jammed into a fissure of the rock on which he was sitting. "Come on, Jim, drop your belts!" Jack ordered when he had recovered his balance. Jim loosened his belts and allowed his holstered guns to drop to the ground. While Jack was gathering the scattered letters together, Jim thought hard. Jack must not find the letters he had hidden. He was sure one of them contained the proof he needed. Suddenly the freckle-faced outlaw laughed aloud. "Jack, yuh sure is a hell of a gun fighter. When yuh slipped, I could have potted yuh easy!" he taunted. Jack Allen started, but made no reply. "I was so darn sure yuh was stalkin' about town tryin' to make yourself tall that I got a bit careless," Jim continued. "What fool idea did you have when yuh done this?" Jack said angrily. "Hell, I was playin' a joke on yuh!" said Jim, with a taunting grin. "Yuh won't think it a joke much longer! Damn yuh! I could have let most things pass, but yuh robbed the United States mails an' you're goin' back with me!" Jack hastily closed the mail sack. He hooked Jim's two gun belts over the pommel of the outlaw's saddled gray and then swung into the saddle. "Yuh climb onto that nag I rode," Jack ordered. "'Fraid I'll run for it?" his twin asked sneeringly. Then the two started back toward town. Jim sighed with relief.