Four world-class undefeated mountain runners compete in the grueling Western States 100-mile endurance race, pushing their limits through challenging terrain to become the last one unbroken.

In 2010, four of the greatest undefeated mountain runners on earth toed the starting line at the Western States 100-mile endurance run, the oldest and most prestigious 100-mile foot race in the world. While their lives may be quite different, the goal is the same: win the Western States 100-mile run. A win will require breaking the course record and running the fastest time in the history of the race. An epic showdown ensues, from Squaw Valley, CA in Lake Tahoe, up though the high snow covered Sierra Nevada Mountains, down through the extreme heat of the American River Canyons and finishing in Auburn, CA. Though all four are undefeated, three must break and only one can remain unbreakable.—Anonymous