Fifteen years before Lewis and Clark, Scotsman Alexander Mackenzie, looking to open up a trade route, set out from Lake Athabasca in central Northern Canada in search of the Pacific Ocean. Mackenzie travelled by bark canoe and had a cache of rum and a crew of Canadian voyageurs, hard-living backwoodsmen, for company. Two centuries later, Robert Twigger decides to follow in Mackenzie's wake. He too travels the traditional way, having painstakingly built a canoe from birchbark sewn together with pine roots, and assembled a crew made up of fellow travelers, ex-tree-planters and a former sailor from the US Navy. Several had tried before them but they were the first people to successfully complete Mackenzie's diabolical route over the Rockies in a birchbark canoe since 1793.
Their journey takes them to the remotest parts of the wilderness, through Native American reservations, over mountains, through rapids and across lakes, meeting descendants of Mackenzie and unhinged Canadian trappers, running out of food, getting lost and miraculously found again, disfigured for life (the ex-sailor loses his thumb), bears brown and black, docile and grizzly.