Just before the boys reached that phenomenon, the marks vanished altogether, coming to an abrupt stop in the snow, but it was evident that this was due to the wind covering the tracks with white crystals from the drifts, and not because the man had mysteriously vanished.
“Well, we may as well go on to the spring,” spoke Fenn. “Maybe we’ll find him there.”
But the vicinity of the mud volcano was deserted, though numerous mud turtles were crawling about over the warm ground, which was devoid of snow.
“I’m going closer and have a look,” decided Fenn, as he started away from his chums.
“Better be careful, Stumpy,” warned Bart. “It doesn’t look as if there had been an eruption lately, and you may catch it all of a sudden.”
“Oh, I’ll chance it,” said the heavy-weight lad.
He walked close to the edge of the spring, which was motionless save for the water that ran from it. Fenn was looking for footprints in the soft ground, but he and his chums had made so many on their own account, on their previous visits to the place, and, as they were still visible (for the ground had not frozen), the amateur detective was at a loss.
“There doesn’t seem to be anything here,” announced Fenn, as he turned to come away. Hardly had he spoken than he was seen to jump back. That is, he tried to do so, but he was too late. An instant later he was observed to throw up his hands and slowly sink into the marshy ground on the edge of the warm spring.
“Help! Help!” cried poor Fenn, as he felt himself going down. “Help, fellows!”