Most of us have lives constrained by the possible. But a brave few reach for what others deem impossible. Some strive to recover from devastating injuries, to balance more people on a thin strand of wire, or to row across more miles than ever before. They put themselves in great danger, sometimes even risking too much. 48 Hours Adventures examines their drive in "Mission Impossible." Kenyans Run Over The Competition: Kenyan long-distance runners have been almost unbeatable. Bryant Gumbel travels to the heights of Kenya to discover what gives these racers their edge. A Fearless Love Of Flying: Patty Wagstaff is one of the best aerobatic flyers in the world. Where many people would be terrified, she finds her happiest moments. Around World In A Rowboat: For years, Mick Bird has dreamed of rowing around the world. Now he's actually doing it. It takes unimaginable willpower, plus 10,000 strokes a day. A Hard Act To Follow: Walther Guerrero lived to perform on the tightrope. Then, two years ago, he had a devastating accident. Harold Dow finds out how he has dealt with life on the ground. He finds a courageous man, unwilling to regret his decisions. A Two-Way Street To Recovery: Picabo Street is trying to recover from a serious skiing injury, her second. Then she meets Rebecca Olivares, struggling with an even scarier, more frustrating injury. See how each helps the other overcome her fears.