“Unbeaten,” the second film from award-winning documentary filmmaker Steven C. Barber, is an inspirational story that chronicles the exploits of 31 paraplegics for six days, as they make their way in wheelchairs and hand cycles in what is known as the toughest road race in the world, “Sadler’s Alaska Challenge.” The course winds 267 miles though the mountain passes of Denali National Park between Fairbanks and Anchorage.