Sutter's Swamp was an area of perhaps a dozen square miles which lay in the Illinois farming country some scores of miles southwest of Chicago, and a few miles east of the modern little city of Brinton. It was a place of almost incredible desolation, considering its nearness to the busy little town, a great, forest-covered tangle of sluggish streams and stagnant pools. Lying in a perpetual twilight beneath its canopy of vine-choked trees, its surface was a confusion of green water and treacherous quicksands and fallen logs, with here and there a mound of solid ground. To most scientists, no doubt, the place would have seemed unpromising enough for a paleontological survey, since never had prehistoric fossils been found in that section. Morton, however, had merely stated in his quiet way that he intended to carry out an exploration of the place, and had departed for it without further announcement.

Arriving in Brinton, quite alone, he had lodged at a hotel and had immediately plunged into his work. Each morning at sunrise he sallied out to the great morass in rough tweed and hip-boots, armed with a long probing-rod of slender steel. To those in Brinton he must have been a perplexing figure, for the great swamp was avoided by them, always, but after a few days they became accustomed to him and took no further note of his comings and goings. And then, a week after his arrival, there burst upon them the sensation of his disappearance.

On that day Morton had set forth for the swamp at sunrise as usual, and one Brinton-bound farmer had glimpsed him entering the western edge of the morass. Through that day nothing further was heard of him, but as it was Morton's habit to linger in the swamp until darkness compelled his return, no anxiety was felt when he was still absent by nightfall. It was only on the next morning, when his absence had lasted for twenty-four hours, that it began to be commented on by some of his Brinton acquaintances.

Discussing it, their doubt and anxiety grew to such a point that shortly before noon two of them drove out to the swamp in the hope of finding some trace of Morton's whereabouts. It was some hours later that they returned, and when they did so they brought with them a tale which spread over the town like flame, and which set the wires between Brinton and Chicago humming with dispatches to the latter city's newspapers.

As told by them, the two had left their car at the swamp's edge and ventured for more than a mile into the morass, without finding any trace of the missing scientist. A mile in, though, they had abruptly come upon some things quite as inexplicable as the absence of Morton. These were great lanes of destruction which some force had torn across the forested swamp, wide paths in which the trees had been smashed down and crushed as though by the passage of some gigantic creature or creatures. And on the mounds and spots of solid ground along these pathways of destruction they had found strange large tracks, which could have been made by no conceivable living creature but which were entirely unexplainable otherwise. Gigantic and five-toed, these tracks were sunken deep in the soft earth, and were each a full square yard in size. Wherever the lanes of smashed trees lay the great tracks had been found also, seeming to lead inward toward the center of the swamp. The two men had stared at these for a time, dumfounded, and then, not daring to venture farther into the gloomy recesses of the swamp, had hastened back to Brinton with their story.

Within minutes that story had spread over all of Brinton, and within hours it was being shouted forth by yelling newsboys in the Chicago streets. In itself the disappearance of so noted a scientist as Morton would have been startling, but coupled with the mysterious phenomena of the swamp it was sensational. By nightfall a dozen reporters and photographers had arrived in Brinton in quest of further details, and with them had come as a representative of the Northcote institution young Edward Rowan, who had been Morton's chief assistant.

Rowan and the reporters found the little town in a state of turmoil that night, the one topic of excited discussion being the phenomena of the swamp. A posse was being formed, they learned, with which to beat the swamp from end to end on the next morning, in the hope of finding the missing scientist somewhere in its recesses. Young Rowan himself instantly volunteered as a member of the posse and was accepted.

To those in Brinton, however, the disappearance of the scientist was almost a secondary consideration beside the strange tracks and pathways which had been found in the morass. Morton's disappearance, after all, might be due to his stepping into a quicksand, but no natural force or forces could account for the lanes of smashed trees and the giant tracks. No animal on earth, of course, was mighty enough to cause those tracks and pathways, yet what could have done so? Was the thing only a practical joke or hoax of some kind?

Until late that night the town's bright-lighted streets remained crowded with unaccustomed throngs of citizens arguing the matter, sometimes heatedly, or exchanging jests concerning it with passing friends. By most, indeed, the matter was treated more as an elaborate joke than anything else, yet one might have sensed also among those shifting throngs an unspoken elation, a curious pride. Whatever was behind the thing, they felt, it was at least bringing fame to Brinton. North and south and east and west, they knew, the wires would be flashing the story. All the nation would read of it, in the morning. And in the morning, too, the swamp would be searched, the thing cleared up. In the morning....

Thus ran the speech and thoughts of those in the streets that night. And strange it seems, to us, that the people in the streets of Brinton could have spoken thus, that night, could have thought thus. Incredible it seems, indeed, that of them all none ever suspected what dark horror out of long-dead ages was even then rising from behind their little mystery, what mighty, resistless menace was even then crashing gigantically through the outside night, to sweep down upon the little town in one great avalanche of destruction and death.