S12, E4: This week, the contestants are surprised by three special guests -- past season contestants Hannah Curlee, Adam Hurtado and Marci Crozier, who each visit and inspire the team that represents his or her respective age group. Then all the players are off to a wild weather challenge in which they have to race while battling the elements -- including wind, rain and snow -- to win coveted letters from home. The winning team receives an unexpected and very emotional bonus prize. Later, trainer Bob Harper takes his team to the pool for last chance workouts, where one player tries to overcome his fear of the water, while trainer Dolvett Quince pushes his team to new heights in the gym and trainer Anna Kournikova takes her team to a favorite spot -- the new "Biggest Loser" tennis court. In the end, the losing team at this week's weigh-in must decide who will be going home. Alison Sweeney hosts the series.