The "unknown trainers" are finally revealed, and both will share their personal stories that led them to "The Biggest Loser." Their contestants, "the unknowns," confront one player they feel isn't working hard enough, and later, "the unknowns" and the ranch contestants square off for a pop challenge. The winning player from each group will get a delicious healthy dinner prepared by Chef Curtis Stone, and compete for a coveted 2 lb. advantage at this week's weigh-in. Later, Dr. Huizenga gives "the unknowns" startling news about their health, and one player is surprised to learn they have the highest percentage of body fat in the group. Meanwhile, trainers Bob Harper and Jillian Michaels single out a few of their contestants to find out what really led to their weight gain, and then the ranch contestants meet host Alison Sweeney for a water-carrying challenge that will give the winner the sole vote at this week's elimination. Later, a surprising weigh-in -- which results in shocking numbers for one team -- disappoints the trainers in a big way, leading to the elimination of one player they feel isn't ready to go home.

The contestants are faced with the "ultimate temptation" this week when each team enters a room filled with each player's favorite foods. Whoever eats the most calories gets to choose which team will go train with the "unknowns" and the new trainers. Later, the stakes are high with a calorie-counting challenge that will give the winners what they want most - letters from loved ones back home. The trainers confront a contestant they think threw the last weigh-in, and later, trainer Jillian Michaels puts trainer Bob Harper through an intense yoga workout to show the players what they'll ultimately be able to do once they lose weight. Then one player takes matters into their own hands to try and send a contestant home.

After four long weeks, the "unknowns" move to the ranch and are reunited with the other contestants, who get to meet the new trainers for the first time. Host Alison Sweeney explains that the ranch contestants will be safe this week if they collectively lose more than 48 pounds, but for the "unknowns," they will be facing their first elimination all season. And both teams only get to see their trainers once this week. The "unknowns" experience some surprises while settling into their new home, and a secret is revealed about how one contestant has lost so much weight. A challenge involving weights shows which team stacks up to be the best, and later, everyone weighs in and finds out whether one or two players will be going home.