At this moment an incident occurred in distant Montana, which, tragic in itself, was not without advantage for Thompson. Captain Lewis, the American officer, had became embroiled with the Blackfeet. They attacked his camp and two of their warriors were killed. Suddenly all the allied tribes were inflamed with the passion for revenge. War parties gathered throughout the plains, and the Piegans in the neighborhood of Rocky Mountain House were drawn off to the south. Perceiving the passes unguarded, Thompson gathered his equipment and made an immediate start. With his wife and children, Finan McDonald and a party of half-breeds to help him, he moved up the river by horse and canoe and entered the mountains. As he advanced, the country became rougher and wilder. The grassy hills were left behind, and the mountains raised their heads in mad confusion height on height, bald and precipitous masses of solid rock, except for the patches of pinewood that clung here and there to their slopes. At times, the crags came together compressing the river to the width of a few yards, through which the current rushed against them. Again, when the valley widened, the stream would divide into many channels dotted with rugged islets and marked by shoals of rock and sand. Finally they reached the valley in which Jaco Finlay had built his house--a low and level plain to the north side of the river, about five miles long and not less than a mile in width. On every hand were to be seen the remains of old tepees erected by the Kootenays, who frequented the spot to make dried provisions from the buffalo and mountain goat. For this reason Thompson gave the valley the name of Kootenay plains. Above Kootenay plains, the river contracted to a width of barely fifteen yards, and so continued to the forks, at which point the canoes had to be laid up. From the forks, there was a splendid view of the mountains still ahead, their peaks more elevated and craggy than they had so far seen, for they were in fact the main range of the Rockies. Taking the left branch of the stream they followed it to within a mile of its end in Glacier lake. At this point, between Mount Balfour on the right and Mount Forbes on the left, was a gap opening to the west. Into this gap they turned. A march of two miles through heavy pinewood brought them to a rivulet whose waters flowed to the west. "May God in his mercy," says the pious explorer, "give me to see where its waters flow into the ocean and return in safety." Thus he marked out his programme for the next four years.