"Keep close inside the yards. We don't want to have him suspect that we're after him."
Frank and Sammy did just as Bob told them to do. Sammy was in his element. He found himself in the midst of a mystery, as he called it, and was greatly excited.
The man they were following kept along the street. The boys skulked from place to place inside of yards and across vacant lots. They knew the neighborhood well, and were never at a loss to get ahead.
When the man came to where the streets were more deserted and the houses further apart, he began to move faster.
"See that," said Bob. "He can walk straight as an arrow when he wants to!"
"Oh, yes, he is just putting on his lameness and all that," added Frank.
"Say, fellows," whispered Sammy, "see where he's going now!"
They had reached the edge of the town. The man ahead of them had crossed a stretch that was a lonely patch of high weeds and bushes.
"He's making for the schoolhouse," said Frank.
"That's what he is," spoke Sammy.
"No—see," added Bob, "he's stopped near the old water hole where they used to graze the cattle."
The three boys were crowded up against a fence, and kept staring after the man and noticing every move he made. He stood still near the spot Bob had mentioned. Then he put his fingers to his lips.
The boys caught the echo of a soft birdlike call. They breathlessly watched the man's figure as it stood outlined against the sky. Then in a minute or two there came a reply to the whistle.
"This is getting exciting," said Frank.
