"On, Jack, what shall I do?" asked Jennie. She was trembling, and seemed much alarmed.

"Do? Why you don't have to do anything," the pony express rider answered. "Let this inspector ask his questions, and then we'll see what course to take."

"Oh, but suppose he finds something wrong—not the proper amount of stamps on hand—I can't be sure I counted them right."

"Say, little girl, don't you worry!" Jack went on. "I don't believe this fellow will do much questioning."

"Why, Jack, what makes you talk that way? He's a government inspector. He told me so! Do you know him?"

"I rather think I do, but I'm not sure," Jack answered. Again there was a grim shutting of his lips, and a determined look came into his eyes. "I want to hear him speak first," the lad said "Then I can tell better."

The inspector, if such he were, had stopped outside the post office to light a cigar. He sat easily on his big horse, and Jack could not help admiring the noble animal. The man himself was a fine physical specimen, but he had a hard, cruel face, and shifty eyes. There was no one in the immediate vicinity of the post office at that time, for Jack had delivered the mail an hour before, and he had sauntered back to the office, after doing some errands about town, to have a talk with Jennie. The other mail would not arrive for another hour, so there was no excuse for the gathering of the crowd which always awaited the incoming mail.

Having lighted his cigar, the man again advanced slowly. He looked all about, Jack thought, to see if he was likely to be interfered with, but this may not have been so.

He dismounted with easy grace, and tied his horse to a post in front of the office. Then he sauntered in. Jack sat down in a chair behind a door, out of sight. He did not want the inspector to see him until the right moment.

"Well, Miss—er—Blake, I believe you said your name was," began the man, and his tone was insolent, "I suppose you are ready to have me go over your accounts now?"

Jack started at the sound of his voice.

"That's the fellow—I'm positive of it!" he thought "Now I've got him—got one of them, anyhow! Oh, this is luck!"

Jack's eyes gleamed.

Jennie hardly knew what to make of the situation. She half expected Jack to do something, or say something, to help her.

Still she was postmistress, and only she was qualified to answer the official questions. But if something was wrong?

"Well, then maybe Jack will help me out," she thought. She was trembling and was much upset. It was the first time an inspector had called at her little office.

"Now, I want to see the records of the registered mail, going and coming, Miss Blake. I also must check over your stamps and cash. Have you had in, lately, any special delivery stuff?"

"Why, yes—that is—Oh, I hardly know where to begin," said the flustered girl, wishing Jack would say something, "You see I've never been inspected before."

"Humph!" sneered the man. "You act as though something was wrong. Most offices where I go don't have such nervous persons in charge. If everything is all right you have nothing to fear. Perhaps you had better step outside and let me go over matters myself. That would be better, and you wouldn't be so nervous.

"If everything is all right you have nothing to fear, and if there is something wrong, well, I'll be as easy in my report to Washington as I can. I won't make it too hard for you. Yes, I think that will be best. Just leave the office to me for a little while."

Jennie flashed, over the man's head, a look at Jack in the corner behind the door. The young pony express rider had arisen, and, to her alarm, Jennie saw his hand go toward the pocket where she knew he carried his revolver—a new one since the robbers had taken his first one.

Jennie wanted to scream.

"Just run along, little girl, and let me have the place to myself," the man urged.

It was time for Jack to act.

He fairly sprang out from behind the door and confronted the man.

"Are you sure," Jack asked, "that if she left the post office to you that you wouldn't run off with it?"

The man started back. He turned a little pale, and then a flood of red surged into his face. He seemed to recover himself with an effort.

"I—I don't know what you mean. Who are you?" he demanded, curtly.

"Never mind who I am, but who are you?" and Jack fairly shot out the words.

"Why, I'm the post office inspector for this district," was the answer, and again the man's tone was sneering. "Are you connected with the department, if I may ask?"

"I am," said Jack, grimly.

"In what capacity?"

"Pony express rider!" shot out Jack. "The same pony express rider that you and your gang of outlaws held up not long ago! I know you now. I was sure of you the minute I set eyes on you on that big horse, and when I heard your voice I was doubly sure. Wearing your mask didn't help any. I know you! You're no more a post office inspector than I am. You're a post office robber, that's what you are!"

The man started to speak, but stopped suddenly. As Jack was about to draw his weapon to order the man to submit, the fellow with a sudden leap was out of the place. In another instant he had jumped to the back of his horse, yanking loose the tie rope as he leaned over the saddle. Then with a clatter of hoofs he was off.

Jennie screamed, but Jack, flashing past her to get outside, yelled:

"Stop him! Get after him! He's one of the fellows who held up the mail, and robbed me! Stop him!"

Jack fired in the air to attract attention, for the neighborhood was deserted. He could not bring himself to fire at the man, nor even at the splendid horse. Though the provocation was great, and though Jack would have been justified, he could not do it.

"Stop him! He's a post office robber!" Jack yelled, again firing a shot Then, leaping on the back of his pony which was waiting for him outside the building, Jack gave chase after the escaping outlaw.

"We've got to get him, Sunger!" he cried. "We've got to get him!"