An elderly curmudgeon lets out a room in his large apartment rent-free to a young student - on condition that she does everything in her power to ruin his son's marriage.

Christian, a visionary scientist, studies wild geese. For his son, a teenager obsessed with video games, the idea of spending a holiday with his father in the wilderness is a nightmare. However, father and son will get together around a crazy project: save a species endangered, thanks to the ultralight of Christian! Then begins an incredible and perilous journey ...