Morning came. At least the dawn was heralded in the east, where the dark clouds turned to pink, growing brighter and brighter, until the sun himself peeped above the horizon.

The posse with which Jack was riding had come almost all the way to Rainbow Ridge, and so far had not had a sight of the robber or any of his confederates, if he had any, which was scarcely to be doubted.

"Well, boys, we may as well go back, I guess," the marshal said. "We'll have to organize a regular hunt, and scatter through the mountains. But we'll have to go back and get some grub. I'm getting hungry, and a man can't hunt a horse thief on an empty stomach."

"That's right!" several of the men agreed.

"Why not keep on?" some one asked. "We can get to Rainbow Ridge quicker than we can to Golden Crossing."

"That's true," added Jack. "I'd ask you all to our cabin, but there's nothing there to eat, since dad is being taken care of by Mrs. Watson."

"Oh, we can get grub easily enough," the sheriff said. "I guess it will be as well to go on to Rainbow Ridge. We want to spread the news there anyhow, and get some men out after the robbers from this end. And I suppose you'll have to report the robbery, won't you?" he asked Jack.

"Yes," replied the pony express rider, and his voice was sad. "I'll have to admit that they got the best of me."

"Oh, shucks! It wasn't your fault at all!" declared the marshal. "Those fellows were bound to get the letters, and if they didn't one way they would another. You couldn't help it."

"But I was asleep right alongside the safe."

"Yes, but maybe they chloroformed you. Such things have been done."

"No, that wasn't done," declared Jack with conviction.

"Well, you'd gone through enough, in that drugging business, to make anybody tired enough to sleep hard," one man said. "They can't blame you."

"No indeed!" agreed another.

But Jack blamed himself. He felt that he had failed in his trust. He did not know what to do. His brain seemed incapable of thinking. If he could only catch the robber and get back the letters!

As he went along with the others over the mountain trail in the early morning, he looked eagerly about, as though he might see some sign of the much-wanted rascal. But the trail was deserted, save for the posse.

They rode into Rainbow Ridge, and that place was soon buzzing with the startling news. As soon as possible a number of men were started out through the mountains, to cover even the bridle paths and trails seldom used. All strangers who could not give a good account of themselves were to be brought into the town.

Mr. Argent was told of the stealing of the valuable letters. He looked grave when Jack explained what had taken place.

"Of course it isn't your fault, Jack," the miner said, "and I'm not in the least blaming you."

"I wanted to come through with them last night, but—"

"It probably wouldn't have done any good, and you might have been attacked and hurt. I'm glad that didn't happen. Of course losing the papers is going to make it very bad for my friends and myself in making good our claim to the mine. But it can't be helped. You did the best you could. No one could have done more. That was a plucky thing you did—tying yourself on the pony's back when you felt you were going to become unconscious."

"But it didn't result in any good in the end," said Jack bitterly. "And now
Sunger is gone, too."

"That's too bad. But still we may catch this fellow. So my package was the only one he took?"

"Well, I didn't stay until all the mail was checked up," answered Jack, "but I'm sure that was missing from the opened safe. I half hoped that this might be another dummy package," said Jack, "and that your other letters might be in the one addressed to the postmaster here."

"No such luck!" exclaimed the miner. "The package addressed to me contained the real and important letters and mine plans that I've been expecting so long. There was some stuff for me in that other package you mention, but it isn't important.

"I wish now," he went on, ruefully, "that I had had a dummy package come through. But I worked that plan once, and I didn't think it would have an effect a second time. Well, it's all in the game, and if I lose this inning I may make it up later. But whatever happens, Jack, don't in the least feel that I blame you."

"Well, it's awfully good of you to say so," replied the pony rider, "but I can't help feeling bad about it."

"Oh, I feel bad myself," the miner said. "But there's no use crying over spilled molasses."

"I think you mean milk," Jack corrected, with a smile.

"Well, perhaps I do. Anyhow the thing to do now is to see if we can't round up these fellows. For there were more than one of them, though you only saw one at the safe. I have an idea who some of them are, too."

As soon as it was seen that a hasty and quick search was not going to result in the capture of the robber and his confederates, a well-planned organized hunt was instituted, to take in as much as possible of the surrounding mountain country. Jack could not take part in this, as he had to ride the express route.

At first he feared lest he might be discharged for having been robbed, but, as a matter of fact, technically he was not in the least to blame. The matter taken was not in his charge, but was in the safe in a post office, and his responsibility ended with the delivery of the mail. Nor was Jennie Blake blamed. The post office authorities did not in the least censure her or her mother. In fact they paid them the compliment, and Jack, too, of saying that extraordinary precautions had been taken, but that the robbery had occurred in spite of them.

Another point was that no express stuff was taken, but only United States' mail. And so the express people had no complaint against Jack, or any one else, as they had lost nothing. Such being the case, there was no good reason for displacing Jack, especially as the robbery had not occurred on his route. So those who hoped to get his position were disappointed.

"You can keep right on riding for us, Jack, my boy," said Mr. Perkfeld.
"We're glad to have you. It isn't often we get as plucky a lad as you. And
when your father gets well, and wants his place back, he can have it, and
I'll find an opening for you on another route, if you like."

"I certainly would like!" Jack exclaimed, warmly.

In addition to the posse organized in Golden Crossing and Rainbow Ridge the post office authorities also sent out inspectors and detectives to try and round up the robbers. This was done the day after it occurred, so that within forty-eight hours the mountain trails were being well patrolled by men eager to apprehend the offenders. And in the mountains, off the trails, were others on the same errand. Jack wished he could be with them, but he had to keep to the mail and express route.

As far as Mr. Argent could learn, no use had yet been made of the stolen documents.

"And that is a good sign," he said to Jack. "I've been in touch with matters, and I and my friends would know as soon as some use was made of them. The people who could best use those documents would have an injunction out against us in a jiffy, and be in possession of the mine as soon as they laid their hands on the papers. But they haven't got them yet, that's sure."

"What does that mean?" asked Jack.

"Just this. Those who would gain the greatest advantage from the possession of our papers, which would give them control of the mine, didn't do the actual stealing themselves. They hired these outlaws to do it, and from the fact that no action has been taken makes me sure that the robber who blew open the safe and took the letters, has not had a chance to deliver them."

"You mean he has them in his possession yet?"

"That's about it, Jack. He is probably hiding out somewhere in the mountains, waiting for a chance to deliver them. He dare not mail them, and he can't get in touch with the rascals who hired him or worked with him. And if any of our men see him first, why we'll save the day yet."

"Good!" cried Jack. "I wish it would be my luck to nab him!"

"Yes. And I suppose you want your pony back?"

"Do I?" cried Jack, and there was no mistaking his longing.

He had provided himself with another horse to ride the mountain trail, and, though it was good, still it was not Sunger.

Mrs. Blake and Jennie were very nervous after the safe robbery, and Mrs. Blake wanted her daughter to give up the post office. But the plucky girl would not.

"They won't bother us again," she said. "It's like lightning. It won't happen the second time In the same place. I'm not afraid, though I am a little shaken."

The damage done by the explosion was soon repaired, and a new and more up-to-date safe provided by the post office department.

It was a week after this momentous occurrence that one afternoon, as Jack was riding along the trail from Golden Crossing to Rainbow Ridge, he stopped to water his horse at the lonely cabin where the old man, on the night of the chase, had told of hearing some one riding past, he thinking it was the pony express.

"Well, Jack," asked the old man, as the lad paused for a moment's chat, "they didn't catch that there safe burglar, did they?"

"No, haven't seen a trace of him, worse luck! Anybody been along to-day?"

"Why, yes, there was a feller here not long ago. He stopped for a drink, and asked for a bite to eat. He looked as if he was in hard luck."

"What sort of a fellow was he?"

"Oh well, I didn't take particular notice. He was afoot."

"Afoot?" cried Jack. "That's queer."

"I thought so myself," agreed the old man. And it was queer to see a man traveling afoot in a country where riding and driving was universal. "I asked him where his horse was, and he said down the road a piece!"

"That was also queer," Jack said. "I wonder why he didn't ride right up here? No excuse for walking when one has a horse."

"That's what I thought," the old man went on. "But I didn't want to ask too many questions. He didn't seem relishin' answerin' 'em."

"Which way was he going?" asked the pony express lad.

"Towards Rainbow Ridge. It wa'n't more'n ten minutes ago."

As Jack rode off a sudden thought came to him.

"I wonder if this could be a clew to the robber?" he asked himself. "Queer thing about his not riding his horse up to Ford's cabin. Why should he do that unless he was afraid the horse would be recognized. Why should he—Great Scott!" suddenly exclaimed Jack aloud. "I believe I know why. He had Sunger, and didn't dare let Ford see him! That's it! I believe I'm on the track of the man who has my pony and the Argent letters!"