gracious! That's queer!" exclaimed Old King Brady, in tones of intense astonishment. "Did you hear it, Harry?"
The boy was thinking.
A startling idea flashed across his mind and he muttered:
"That cry was uttered by the same person we heard in New York, and I'm convinced that it was the man called Albert Reid."
"But he was murdered – "
"You only suppose so. There was circumstantial evidence that he was. But after all he may yet be alive."
This was a startling view to take of the matter.
Old King Brady shot a quick glance at Harry and exclaimed:
"You may be right. The man in the box may not have been dead after all. Perhaps he was alive, under the influence of a drug. The man who drugged us may have drugged him, too, you know.
"Hark!"
A chorus of fierce cries came from the hut.
There was the noise of a scuffle, then a voice which sounded very much like that of a negro roared in furious tones:
"Keep still, or I'll kill you!"
Old King Brady rose to his feet, very much agitated.
"I can't stand this much longer, Harry!" he muttered.
"Come on to the hut and we'll investigate the row," replied the boy.
Casting aside all caution, they rushed toward the old building.
Not half the intervening distance had been covered, when suddenly the noise ceased and the light went out.
The detectives halted.
"Were we seen?" panted Harry.
"Perhaps. Listen a moment."
They remained perfectly still and the trees cast a dark shadow over the scene which the moon could not dispel.
Five minutes passed.
Hearing and seeing nothing unusual, Harry said:
"Come on."
"Wait till I light my lantern."
"I'll stand guard with my pistol."
Old King Brady drew out a match and lit his bull's-eye.
Moving forward, they reached the hut and made a circuit of it.
The door was wide open.
They boldly entered the building.
It contained only one room, and to the amazement of the officers, it was empty.
Staring around, Old King Brady observed that there was only one door and the two windows they had been watching – one at the rear and the other at the side of the little building.
The door was at another side.
"Gone!" ejaculated the old detective.
"Where?" asked the astonished boy.
"Heaven only knows."
"Search outside."
Old King Brady dashed out the door.
He saw by the moonlight that the little island on which the hut stood was in the midst of the swamp.
If any one left it, he was bound to see them.
But not a soul met his view.
No one could leave the hut, cross the swamp and reach the mainland so quick that he could not see them escaping in such a short space of time.
Yet he failed to see any one in the swamp.
That convinced him that no one left the oasis.
And nobody was on the solid island of earth.
He could not have failed to observe them if they were there.
"What the deuce does this mean?" he gasped in bewilderment.
Then he finally returned to his partner.
"See any one?" eagerly asked the boy.
"Not a soul. And you?"
"I've searched this place, but no one is here."
"Then where did they disappear to so mysteriously?"
"Blessed if I know."
"You heard two human voices here, didn't you?"
"Of course I did."
"Have you thoroughly examined this place?"
"Every inch of it, and couldn't find them."
Old King Brady made a round of the room and came back.
He plainly saw that the walls were not double, and that the floor was merely covered with common dirt.
There was not a piece of furniture nor a lamp in the place.
Yet the detectives had seen a light distinctly.
"They ain't here, sure enough," said the old detective, "and they didn't leave here. Now, how could they vanish, and where did they go?"
"I'm completely rattled. Beyond my depth entirely."
"So am I. This mystery is too much for me to solve."
"See! Daylight is breaking."
"Let's search the place again."
They went at it with renewed zest, and spent two hours vainly searching for the means those speakers employed to drop out of sight.
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
