In an abandoned hotel, a man's eyeballs are discovered, with the words "He saw it!" written beneath them in blood. Before Chief Inspector Marc Davids and his colleague Zoé Martin can even follow up on a lead, a YouTube video goes viral on social media. It shows the crime scene, the investigators, all the gruesome details—everything but the murder itself. Shortly after, another murder. Another bloody message. A new video. Did the killer film the videos? Is he challenging the police? Or is the murderer himself being stalked by a deranged YouTuber?