In the summer of 2014, a young German tourist sat alone in a Bulgarian airport waiting for a flight home. He never boarded it. What the CCTV captured in the moments before Lars Mittank vanished — the sudden panic, the sprint through the terminal, the abandonment of everything he owned — has haunted the internet for a decade. Was someone following him? Or was it something no one else could see? Whatever Lars believed in that moment, it was enough to make him run. And he never came back.