“Those fellows must know this river,” remarked Sam, as he started to lace his shoes, there being nothing else just then to do.

“They ought to—­if they are the fellows who visited our henhouse before,” answered Tom.  “Dick, can you see them?”

“No, but I know they must be ahead.”

“Perhaps they went ashore—­just to fool us.”

“They couldn’t get ashore here very well—­it is too rocky, you know that as well as I do.  Listen!”

They listened, but the only sound that broke the stillness was the distant roar of Humpback Falls, where Sam had once had such a thrilling adventure, as related in “The Rover Boys at School.”  Even now, so long afterward, it made the youngest Rover shiver to think of that happening.

A minute later the boat came clear of the tree shadows and the boys saw a long stretch ahead of them, shimmering like silver in the moonbeams.  Sam, looking in the direction of the opposite shore, made out a rowboat moving thither.

“There they are!” he cried.

At once Dick essayed to turn their own craft in that direction.  But with only a bit of a board for a paddle, and with the current tearing along wildly, this was not easy.  The rowboat was turned partly, but then scraped some rocks, and they were in dire peril of upsetting.

“I see where they are going!” cried Tom.  “To the old Henderson mill.”

“We’ll have to land below that point,” said his oldest brother.  “If I try to get in there with only this board I’ll hit the rocks sure.”

“They are taking chances, even with oars,” was Sam’s comment.  “See, they have struck some rocks!”

He was right, and the Rovers saw the boat ahead spin around and the two men leap to their feet in alarm.  But then the craft steadied itself, and a moment later shot into the shadows of the trees beside the old flour mill.

It was not until five minutes later that Dick was able to guide their own rowboat to the shore upon which the mill was located.  They hit several rocks, but at last came in where there was a sandy stretch.  All leaped out, and the craft was hauled up to a point out of the current’s reach.

“Now to get back to the mill as soon as possible, and corner those fellows if we can,” said Tom, and without delay the three Rover boys started through the woods in the direction of the spot where the two men had landed.

CHAPTER V

AT THE OLD MILL

The Henderson mill was now largely so only in name.  So far back as the Rover boys could remember, it had been a tenantless structure going slowly to decay.  The water wheel was gone, and so were the grinding stones, and the roof and sides were full of holes.  Henderson, the owner, had years ago fallen heir to a fortune, and had moved away, leaving the building at the mercy of the tramps who frequently stopped there.