On a bridge near Puebla, Mexico, French skydiver and base jumper Remi Angeli faces his biggest challenge yet. He wants to try a "gainer" for the first time. That means he has to jump forward and roll backwards in the air at the same time. Like a backflip—but in free fall. This manoeuvre requires precise physical control and very steady nerves. In theory Remi has both, but in practice, it's a completely different story.