The final four contestants go home to prepare for a marathon, but some of the players have trouble staying on track when surrounded by all of the distractions of home. And one contestant gets a special visit from chef Curtis Stone. Later, they return to the ranch to run the 26.2 miles, cheered on by family members as well as each of their favorite past season contestants - season 5 winner Ali Vincent, Season 2 winner Matt Hoover, and Season 7 contestants Mike Morelli and Sione Fa. The winner finishes in record time, breaking a "Biggest Loser" marathon record. Then it's the very last "last chance workouts" with trainers Bob Harper and Jillian Michaels before a final weigh in determines who the two definite finalists will be - and which two contestants fall below the dreaded yellow line, leaving America to vote which one will be the third finalist to compete for the grand prize of $250,000.

After viewer votes determine the third finalist, the winner of the $250,000 prize is crowned in the Season 9 finale. The eliminated players also return to weigh in for the $100,000 at-home prize, and former contestants share their weight-loss progress since leaving the show.

Season 10 kicks off with a new theme of "paying it forward" and 21 contestants vying for a spot at the ranch to get healthy and change their lives forever. With obesity now one of the leading causes of preventable death in the United States, "The Biggest Loser" wanted to broaden their reach this season, pay it forward and motivate communities - not just contestants - to get healthy. So trainers Bob Harper and Jillian Michaels and host Alison Sweeney travel to seven cities in the premiere episode, with each trainer leading community fitness challenges like a one-mile race or a 500 step-up competition. In each of the seven cities - Detroit, Los Angeles, Portland, Atlanta, Phoenix, Oklahoma City and Boston - there will also be three contestant hopefuls competing in the challenges. The two candidates who complete their fitness challenge first win a spot at the ranch, while those who don't make it will get a chance to vie for a spot on the show in a later episode. Guest starring in the premiere will be three popular past season contestants -- season eight winner Danny Cahill, season seven finalist Mike Morelli and season five finalist Mark Kruger.