Louis Antioch, a young scientist-philosopher, receives a strange proposal from a friend of his adoptive parents, the famous Swiss ornithologist Boehm: to trace the migration path of storks and try to find out why several hundred ringed birds did not return to Europe, to their native nests. On the eve of his departure, Louis finds Böhm dead. The circumstances of the ornithologist's death seem suspicious to him, and he decides, no matter what, to complete the planned trip. Within a few days, Louis realizes that his trip is a very risky undertaking.