That night Gus came over to Bill’s home and the two went over the plans until late; then Gus chatted awhile on the steps, Bill standing in the doorway.  Suddenly, from over toward the northeast, in the direction of the upper tract of the Hooper estate, there was a flash in the sky and a dull reverberation like a very distant or muffled blast.  Bill was talking and hardly noticed it, but Gus had been looking in that direction and, calling Bill’s attention, wondered as to the cause of the odd occurrence.

In the morning, as the boys descended the hill, George, who was always on hand half an hour ahead of time, came up to meet them and was plainly excited.

“Mist’ Bill an’ Gus, de dam’s done busted a’ready an’ de water’s jes’ a-pourin’ through t’ beat ol’ Noah’s flood!  Whut you ’low was de because o’ dis givin’ way?”

“By cracky, Bill!” was Gus’ comment as they stood looking at the break which seemed to involve a yard square of the base and cracks, as though from a shock.  “You know and I know that the water didn’t push this out.  How about that flash and bang we heard last night?”

“I can’t see how the water could have done it,” said Bill, who evidently had more talent for construction than for determining destruction.

“There’s something behind this that I don’t like and I’m going to find out about it,” said Gus, his usually quiet demeanor entirely gone.  “You ought to be able,” he continued, “to put two and four together.  How about that warning Grace gave you?  And how did she know anything out of which to give it?  And why wouldn’t she give any names?”

“Well, I have wondered; I thought I saw why,” Bill said.

“Of course you see why, old scout.  And if you’ll leave it to me, you’ll know why and all the how and the what of it, too.”  Gus was never boastful; now he was merely determined.

The boys opened the flood gate and after the water no longer flowed through the break, they began a closer examination that surprised them.  Mr. Hooper, Thad, Grace and Skeets descended the hill.

Bill, after greetings, merely pointed to the break.  Mr. Hooper started to say something about the structure’s being too weak; Thad laughed, and Grace, looking daggers at him, turned away and pulled Skeets with her.  Gus, gazing at Thad, addressed Mr. Hooper.

“Yes, too weak to stand the force of an explosion.  It wasn’t the water pressure.  Mr. Hooper; you’ll notice that the stones there are forced in against the water; not out with it.  And the cracks—­they’re further evidence.  We heard the explosion about eleven o’clock; saw the light of the flash, too.”

“Shucks!  You reckon that’s so?  Got any notion who it was that done it?”

“Yes, sir; got a big notion who it was; but we won’t say till we get it on him for sure.  And then’s it’s going to be a sorry day for him.”

Gus was still gazing straight at Thad and that youth, first attempting to ignore this scrutiny and then trying to match it, at last grew restless and turned away.  Mr. Hooper also had his eyes on Thad; the old gentleman looked much troubled.  He raised his voice loud enough for Thad to hear as he walked off: