Jack saw that he could not hope to overtake the man ahead of him by an ordinary chase. The horse the pony rider bestrode was not fast enough. And a short distance ahead was a place on the trail where the suspect could escape by a side path.
"Here goes!" murmured Jack.
In his loudest voice he cried out:
"Whoa, Sunger!"
Something happened at once. The pony, which had been running his best in order not to let the horse behind pass him, pulled up so short that the man was flung with great force from the saddle, and over Sunger's head. Over he went, vainly trying to save himself, and the next moment he landed heavily on the side of the trail and did not move.
"Well, I guess that ends your riding for a time," thought Jack, grimly. Then he rode forward while Sunger, with a whinny of delight, turned back to meet his master.
"Oh, Sunger! Sunger, old boy! You did it!" cried Jack. Then his heart smote him as he saw the motionless figure beside the trail.
Pausing only a moment to caress his recovered pony, Jack hastened to the side of the man who had been thrown off by Sunger's sudden stopping. The fellow was a stranger to Jack, who could not tell whether or not he was the post office robber. The man was unconscious, and, with little compunction, Jack rapidly searched through his pockets.
In an inner one he came upon a package. With beating heart Jack pulled out the bundle. He knew it in a moment. It was the packet of letters addressed to Mr. Argent. A look at the seals convinced the lad that they had not been broken.
"Talk about luck!" he cried, "I'm certainly in it to-day! I've got Sunger, got the papers back, and caught the robber, too. At least I think he must be the safe-cracker, though I can't be sure. I've got him right! Sunger, old boy, we worked the trick to perfection!"