The leaders approach the finish line and the battle for first position heats up. Allen Moore passes Brent Sass with a two-minute lead as they prepare to leave the last checkpoint. More than 300 miles now separate the first and last teams. One by one the remaining teams attempt the biggest challenge of the race, Eagle Summit. During the ascent Normand Casavant complains of unsportsmanlike methods from Damon Tedford. Teams jockey for positions and the larger share of the purse. Will the trail take more victims? Will there be more surprises before the finish line?

The gaps between teams continue to widen. The last teams finally arrive in Dawson City as the first teams reach Eagle, Alaska. The tiny isolated village has no road access in the winter so handlers must take a 24 hour detour to meet their teams at the next checkpoint. Two more teams scratch at Eagle, but without road access their dogs must be evacuated by plane. Only 16 teams remain. Mushers begin to make mistakes as sleep deprivation sets in. Leader Brent Sass stops on the trail for a short nap and sleeps away 9 of his 10-hour lead. Will it cost him the race? The second half of the trail holds even more dangers than the first including the infamous Eagle Summit. Who will ascend the summit and who will fail?

Teams reach the historic Gold Rush town of Dawson City, Yukon. There is a mandatory 24 hour layover here for mushers and dogs to rest and refuel. The handlers setup camps to care for the dogs. This is the only time during the race where the handlers are allowed to feed and care for the dogs. Normand Casavant walks us through the strategies for packing dozens of bags of food and supplies that are distributed to each checkpoint for each team. The extreme conditions and -50 degree Celsius temperatures force another 3 teams to scratch. Brent Sass already launched in the second part of the race and encounters a moose. Will he escape the largest living threat of the Yukon Quest trail?

It's early morning at Pelly Crossing and the problems multiply. Matt Hall, third place and Rookie of the Year from 2014, is in rough shape. The jumble ice has hurt his team and he must leave behind 5 dogs. Jason Campeau's sled got so badly damaged that he may have to replace it and take an 8-hour penalty. Kristin Knight Pace is the last to leave Pelly Crossing and has dropped from 12th to 26th position. We begin to see why the Yukon Quest has the reputation as the toughest sled dog race in the world as 5 teams scratch and drop out of the race. Normand Casavant explains the universal language used in sled dog racing. Hugh Neff shares the challenges of feeding a 10,000 calories a day diet to a team of 14 dogs. Brent Sass wins the Dawson City prize, a 4 ounce gold nugget, for being the first to arrive at the midway checkpoint.

Teams begin arriving in Carmacks, the second checkpoint. As temperature fall to -50 Celsius technologies starts to fail. The GPS trackers that allow race officials and volunteers to predict the mushers' location and arrival time malfunction. The gap between teams begins to widen as mushers leave for the third checkpoint: Pelly Crossing. It's a treacherous 73 miles along the Yukon River trail. The major obstacles like open water and razor sharp jumble ice take a toll as some mushers must abandon the race.

The first leg of the race is fast and furious and the rankings are constantly changing. We ride along with some of our mushers to see the techniques they use to train their teams. We also shatter the myths about the health and care of sled dogs and see the race veterinary team at work. Allen Moore starts in first position and against all expectations arrives in Braeburn in 23rd. Every team must check in and pass a veterinary exam. Some will decide to take their mandatory layover here to rest and replenish their supplies. Others, Like Hugh Neff, make a run for Carmacks, the second checkpoint. He started the race in last position but has blasted past the entire pack to take the lead. Can he sustain his lead?

Excitement builds as mushers approach the starting line of the Yukon Quest. Nobody seems deterred by the sunny -48 degrees temperatures. The teams leave at 3 minutes interval for the first checkpoint, Braeburn, located 100 miles from Whitehorse. The historic trail needs to be prepared before the race each year. Bob Daffe and a team from The Canadian Rangers Patrol Group are tasked with taming the dangers of the race route. We discover the strategies to breed the fastest dog teams.

Preparations for the 31st edition of the Yukon Quest has begun. The toughest sled dog race in the world attracts a very special bread of competitors. Veterans like Brent Sass, Hugh Neff, Allen Moore and Normand Casavant and rookies, like Matt Hall, Jason Campeau, Damond Tedford and Kristin Knight Pace are all drawn in to the challenges of the long-distance sled dog world. Our characters share their fears and excitement about competing in this historic race. What they all have in common is a passion for adventure and a love of dogs. Who among them has what it takes to win?