Finally he said in sarcastic tones:

"Well, how do you like dying by inches?"

"This was cowardly of you, Mason," said Old King Brady, bitterly.

"It's my way of gaining revenge."

"Why don't you give us a fair show to fight for our lives?"

"Because you are so dangerous you might beat me."

"Help us out of here, and act like a man."

"I won't. See all the harm you've done me. In the first place, you've cheated me out of a fortune. In the second place, you prevented me from getting the girl I loved. In short, you've baffled me at every turn, after I made the most elaborate preparations to succeed."

"We did our duty."

"Oh, that be hanged! You'd kill me to do your duty, and I'm justified in ridding myself of such enemies as you two are."

"If you hadn't done wrong you would not have had us after you."

"Well, I know that very well. It's stale news. But I had an object in what I did, and you interfered and foiled me. I didn't do any one much harm, and----"

"You robbed Oliver Dalton and put him out of the way."

"Robbed him?"

"Yes. You pilfered money from the mail."

"How do you know I did?" asked Mason, with a startled look.

"Dalton employed us to expose you, and we'd been at his house on the night you and Johnson were posing in Thirty-sixth street as undertakers."

"The deuce! I didn't know Dalton knew."

"You admit, then, that you did rob his mail?"

"No use denying it now," laughed Mason. "I freely admit that I did get away with thousands of his dollars in that way. No use trying to conceal it. You'll never get out of there alive to prosecute me. And even if you do, you've got enough other evidence against me to send me up as high as a kite."

Despite his peril Old King Brady felt triumphant.

They now knew who the mail thief was.

By this time the Bradys were sunk in the quick-sand to their hips, and were unable to move in any direction.

They kept sinking every moment with horrible rapidity.

"Well, we can't arrest you now for that crime," said Old King Brady, "but I've got a feeling that we shall do so yet."

"Humbug! You are getting dopy. You can't escape from there."

"Are you going to abandon us to our fate?"

"Yes; I wish you a merry voyage over the River Styx!"

And with a mocking bow and a jeering laugh, he strode away.

The Bradys began to shout for help again, and Mason paused, and, darting an angry look at them, he shouted threateningly:

"If you don't shut up we'll shoot you!"

"So much the better," replied Old King Brady. "It will end our misery."

"Oh, we won't shoot to kill," growled the scowling rascal, "but we will riddle your carca.s.ses with painful wounds."

"Mason, you're a fiend."

"Am I? That's a compliment."

And with a short laugh he disappeared in the bushes.

Once more the detectives began to call for a.s.sistance, for they now were sunk to their armpits in the sand.

Their voices sounded hoa.r.s.e and smothered, and a despairing feeling was creeping into their hearts, but they kept on shouting.

Presently Mason shouted at them from the bushes in angry tones:

"Are you going to shut up?"

"No!" roared Old King Brady.

"Then I'll pepper you!"

And bang! went his rifle, and a bullet whistled by their heads.

"Keep on yelling, Harry!" gasped the old detective.

"Help! Help!" shouted the boy, obediently.

Bang! went Mason's rifle again.

The ball grazed Harry's cheek, and stung like a bee.

Just then the shots and yells were heard by an old track-walker of the railroad, and he rushed around the swamp shouting:

"All right! I'm coming!"

This unwelcome voice to Mason caused a look of alarm to flit over his pale features, and, fearing arrest, he sped away.