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.