In April 1978, in the small town of Pößneck, Thuringia, a teenager, Lukas Keller, attempts to escape East Germany by riding a bulldozer through the Inner German Border Zone. However, he is shot by automatic machine guns and left for dead by the guards; his family is informed while having a picnic with their friends, the Strelzyks and the Wetzels, and the entire Keller family are taken away by the police. Finally fed up with his life under the GDR regime, Peter Strelzyk proposes a daring plan to his friend Günter Wetzel: they will build a balloon to carry themselves and their families (eight people total) over the border to West Germany. They purchase 1,255 square yards of taffeta (claiming it is for a camping club); Günter sews the fabric together with a sewing machine in his attic and Peter experiments for months to construct a hot air balloon burner. Of course, they face setbacks: fires while trying to inflate the balloon, struggles to build a burner with sufficient power, extremely suspicious neighbors, and doubts about the plan's workability from Günter's wife, Petra.