Contestants Tackle One of the Biggest Challenges in Show's History

After revisiting the hospital to check in on their progress, the remaining players face off in one of the biggest challenges in "Biggest Loser" history -- they must fly across a ravine on zip-lines and collect flags. One player gets the chance to give immunity to himself or one of his teammates, and his decision ultimately affects his own fate. And a shocking announcement at the weigh-in changes the way the rest of the game will be played.