Finally they desisted.

The great swamp mystery was too much for them.

By this time the sun had risen and flooded the scene, dispelled the vapors that hung over the bog and lighted up the surrounding country.

"We'd better get out of here," said Old King Brady. "I see a fine old residence over there on the mainland. Let's get over there and get our breakfast. I'm going to keep at this swamp till I solve that mystery."

Crossing the board walk, they made a detour and reached the house.

It was a fine country residence with many acres of ground, part of which was formed by the swamp.

They Saw a big negro in overalls standing at the gate and Harry asked him:

"Say—who lives here?"

"Oliver Dalton, the Broad street broker, sir," replied the colored man.

This reply startled the detectives, for the owner was the very man whose case of mail robbery had been placed in their hands.

They glanced significantly at each other, and that look spoke volumes.

CHAPTER IV.

THE DISAPPEARANCE OF MR. DALTON.

"See here, my friend," said Old King Brady to the darky, "do you know anything about that little hut standing out there in the swamp?"

"Dat hut? Sho'. Nobuddy nebber go in no mo'. Useter be fo' Massa Dalton when he go out shootin' reed birds."

"Then it isn't in use any more?"

"No, sah."

"Does Mr. Dalton live here all the year round?"

"Golly, no. Only in de winter. Comes heah wif Missy Lizzy an' his nephew, Ronald. Me an' my ole gal keep de house fo' dem de rest ob de time."

"I see. Then you don't expect them here for a long time, do you?"

"Dey only jes' lef' heah las' month, an' went back to York. But Lawdy, whut should Massa Ronald do but come back all ob a sudden las' night wif dat ornary niggah cuss, Sim Johnson, an' git bilin' drunk, an' dey gwine out an' didn' come back till de roosters crowed dis mawnin'."

"Who is Sim Johnson?"

"Massa Dalton's valet."

"And does the broker know his nephew drinks?"

"Mah goo'ness, no. If he did, dey would be a fight sho's yo' bo'n, sah."

"Is Ronald Mason in the habit of going on sprees with his uncle's negro valet?"

"Nebber done seed dem so thick befo'."

"Does he intend to remain here long?"

"Spec's not, kase dey didn't bring no luggage."

"Did they explain why they came back so unexpectedly?"

"Not to me."

"I'd like to see Mr. Mason."

"Better come back later, sah. He am too full now."

"Very well. What's your name?"

"George Scott."

"Can you tell me where we can get our breakfast?"

"Right heah, if yo' like, sah."

"Thanks. We'll accept and pay you for your trouble. Is there a town near?"

"De railroad station ob Swamp Angel, two miles down dis road."

"I suppose we could find board there?"

"Yassah. Dar am a little hotel neah de depot. Come in, sah—come in."

He led the detectives up a path to the house and when they were seated in the kitchen, his big, fat wife, Dinah, bustled around and soon had a savory breakfast set before them.

The detectives praised her cooking and paid the old servants so well for their attention that the faithful pair voted them as fine gentlemen.

Soon afterward the detectives started for Swamp Angel.

"The action of Ronald Mason in coming here so oddly with his uncle's valet strikes me very strangely," remarked Old King Brady, as they trudged along the road toward the station. "In fact, it is a most singular proceeding. He evidently poses before his rich uncle as a paragon of virtue. Behind the old man's back he is evidently a high roller."

"Then he must be a deceitful man," said Harry.

"Of course, for he's deceiving his trusting uncle."

"You are suspicious of him, ain't you?"

"Well, yes. It takes plenty money for a young man to lead a riotous life. If Mason draws a big salary in his uncle's office, where he is employed as a clerk, he may be able to afford it. If he is poorly paid, he may be at the bottom of the mail robberies we were called upon to investigate. See the point?"

Harry nodded and smiled; then he thought for a moment.

"You're pretty keen," he remarked. "It's a fair presumption, though."

"I think we had better keep an eye on that frisky young gentleman when we return to New York," continued the old detective, wisely. "It may lead to a solution of the problem we are so anxious to solve for the broker."

"Are you going back to Dalton's to see him?"

"Yes, this afternoon. I merely wish to size him up."

"How long do you intend to remain here?"

"I'd like to unravel the great swamp mystery before we go."

"Perhaps we may in a few days."

"Well, we'll give the matter a fair trial, anyhow."

Upon reaching Swamp Angel, they soon located the little hotel and there turned into bed for a few hours' sleep.

It was late in the afternoon when they returned to Dalton's.

Here they met the old negro again and he said:

"Yo's come back too late, gemmen."

"How so?" asked Old King Brady, in puzzled tones.

"Massa Mason an' Sim done gone an hour ago."

"Where to?"

"York."

The detectives were keenly disappointed.

However, they did not complain, and went away to search the swamp again for some trace of the missing body.

No success crowned their efforts.

In fact, after a useless search, covering a period of three days, they at length gave up the hunt in despair and returned to New York.

It was useless to remain prowling around that bleak swamp trying to dig up a mystery that baffled all their ingenuity.

"We went beyond our depth," said Harry, when they reached New York. "The game was too hard to solve. The mystery of the murdered man in the box must remain unsolved. It can go on record as one of the many strange cases that have baffled the detectives before. It's our duty now to report the matter to our chief, drop it, and resume our attempt to locate the broker's mail thief."

"Then come to headquarters at once," said Old King Brady, as they left the cars.

They met the chief in his office and he smiled pleasantly, and asked:

"Well, where have you two been keeping yourselves hidden during the past week? I haven't seen or heard from you lately."

The Bradys told him what they had been doing.

He listened attentively, with a grave look upon his face, while they were giving him the facts, and said when they finished:

"Then that murder mystery was too much for you, and you went beyond your depth trying to solve it, eh? Well, it's just as well you let it drop."

"Anything new going on?"

"Yes. Something relating to your mail robbery case."

"Indeed! What was it?"

"Oliver Dalton has disappeared."

"Where to?"

"Nobody seems to know."

"That is very strange."

"You had better go up to his house and get the particulars from his daughter. She is frantic to find her father. Some points might be gained in the broker's Broad street office."

"We'll follow your advice, sir," said Old King Brady.

The chief did not seem to have many facts in relation to the case, so the detectives finally left him.

Going to the broker's office, they found it occupied by half a dozen clerks.

Having asked for Mr. Dalton, the office boy said to them:

"You'd better see Mr. Mason about that matter, sir."

"Is the broker's nephew in?" asked Harry.

"Yes. He's the boss here now. Got your card?"

Harry handed him a business card and he carried it into a private office in the rear. A few minutes later he came out, with a smile on his face, and said to the detectives:

"Mr. Mason says for you to come in."

He ushered the Bradys into the private office and they there beheld Ronald Mason, the broker's nephew, sitting at his desk.