Even while Sandy was shouting these thrilling words, a figure flitted past Bob and Simon Kenton. It was the agile Frenchman, and he was making at full speed for the shelf where the exit of the strange cavern lay.
Abijah Cook, aroused by the cries, scrambled to his feet, being doubtless under the impression that they had been attacked by a large force of the dusky enemy, against whom his hand had been pitted in continual warfare.
There was a collision, and the borderer measured his length again on the stone floor of the cavern. The fleeing form of Armand Lacroix was just glimpsed as he shot around the corner of rock that lay between the rear part of the cave and the waterfall.
For once Kenton did not happen to have his rifle with him, since he had no reason to dream that he would need it. His first act had been to leap wildly forward in the hope that he might yet snatch the weapon up before the Frenchman could vanish beyond the outcropping of rocks.
Bob had seen that, when Lacroix regained his feet after his collision with Abijah, he held something in his grasp that had not been there before. It was the weapon of the big borderer, which doubtless the cunning French trapper had made up his mind to snatch up even before he started to escape.
Kenton knew just where his own rifle was leaning against the wall, and, as he reached the spot, he snatched it up with a single movement. Then he went flying after the figure of the Frenchman, leaving the two boys dumb with fear lest their plans were now doomed to utter defeat.
Larue and his two companions had witnessed with mingled feelings this dash for liberty on the part of Lacroix. They exchanged many low mutterings among themselves, and, while neither of the boys could understand much French, they felt sure that Larue was furious because the other had not waited to cut their bonds before dashing off, and thus giving them a chance to escape also.
"Oh! what if he gets clear away?" said Sandy, when several minutes had passed, and Kenton did not return.
"I hope that may not be," Bob remarked between his set teeth. "For his first act will be to bring the Senecas against us, and, even if we managed to escape, think of what Kate's fate would be."
"Hark!" cried Sandy, gripping his brother's arm convulsively; "did you hear that, Bob?"