Pierre has to leave with the voyageurs, to be the only source of income his family has. It would have been his father's job like normal, but his father got injured while cutting wood, chopping his thumb off, making him unable to paddle the canoes. In his place, Pierre goes.
Pierre is doing pretty well. He gets along with most of the men, just the occasional teasing, same as anyone, except Beloit. He constantly makes fun of Pierre's blistered, swollen, and pained hands, and sore muscles, plus an endless list of other things. Pierre really wishes he could go back to the comfort of his classroom, and home with his family.
Pierre's brigade took to the rapids, and I'm guessing they regret it. One turn too soon, ended up getting them stuck on a rock, about to get hit by another canoe. La Londe sacrifices himself to get the canoe unstuck, and they are unable to find more then his broken oar, before they have to leave.