The race to St John's continues as the five pairs leave the indigenous island of Haida Gwaii and head into the wild, navigating their way into the heart of the Yukon to the second checkpoint, Dawson City, a former boom town established during the Klondike gold rush of 1898.

Getting to Dawson means completing a journey of over 2,000km north up one of the most isolated highways in the world, the vast wilderness only occasionally broken by the odd small settlement or truck stop. The racers have to negotiate dense forests and vast ice fields, all with next to no public transport.

Claudia and her dad Kevin are the first to leave. After a budget-busting taxi ride in the previous leg, they opt for a no-frills strategy of camping and car-sharing. Best friends Tricia and Cathie set off again with self-confessed control freak Cathie anxious about venturing into the unknown and being reliant on others. To get them to Dawson City, married couple Zainib and Mobeen continue to rely on the kindness of strangers and hope to save money by ride-sharing their way to the checkpoint.

Having never owned a backpack prior to setting off from Vancouver, Monique's education continues, and the leg gets off to a difficult start when she has to camp for the first time. Estranged brothers Marc and Michael leave the checkpoint in last place, and things go from bad to worse when Marc's fear of bears causes a spat between the pair. After a slow start, they try out an alternative approach to the race and focus on getting to know each other as brothers.

Five teams have been set the challenge to race across the breadth of Canada, passing through seven checkpoints, taking them from the Pacific coastline to the edge of the Arctic and the shores of the Great Lakes, ending up at their final destination on the Atlantic Ocean, St. John's on the island of Newfoundland, the most easterly town in North America. A £20,000 cash prize is at stake.

The remaining pairs must now navigate to the fourth checkpoint, the remote outpost of Churchill, where polar bears can outnumber people. On Hudson Bay, at the edge of the Arctic, Churchill is not connected to the rest of Canada by road but by a twice-weekly train, and the teams have just three days to catch it. It's a journey that will take them from Alberta's major cities of Calgary and Edmonton, before the Rockies make way for Saskatchewan's great prairies and badlands.

As the train makes its way from Winnipeg to Churchill, the teams need to work out where they can catch it. With the clock ticking, every decision counts for the racers, as they work together once again to reach that all-important checkpoint to be one step closer to the finish line and the £20,000 cash prize.