In another hour they had reached Chicago, and the brief glimpse they got of the great city by the lake made them wish that they could stay over a day and explore its wonders. But their tickets called for a continuous trip and in a little while they were leaving the city behind them and rushing over the last stage of their journey.
The cities were less frequent now, great stretches of prairie land became more and more common, and the boys realized that they were getting into the heart of the real West, the region of boundless plains as contrasted with that of crowded towns.
Little else occurred outside of their own plans and fun to interest the boys until they were getting close to Grand Forks, where their railroad traveling would come to an end.
But when they were two hours east of Grand Forks, four men, who aroused Sammy's curiosity at once, boarded the train at a little station.
They were rather rough-looking men, and Sammy thought that one of them in particular had a villainous look. The other boys set them down as surveyors or prospectors, but such a commonplace idea had no charms for Sammy.
"I tell you there's something queer about them," Sammy persisted. "Do you see that black box they're so careful about?"
"Well, what of that?" said George, carelessly. "That may have some of their instruments in it."
"It looks more to me like an infernal machine," said Sammy, darkly. "That's why they handle it so carefully. It might go off if it got a hard knock. I tell you I believe those fellows are up to something."
"Some more murderers perhaps," put in Bob. "You'd better listen mighty close, Sammy."
"Never mind," said Sammy, stubbornly. "Because I made a mistake once doesn't say I'm wrong this time. I'm going to keep my eyes on those fellows until we get to Grand Forks."