Brussels. Leo is a Spanish subway driver. When he was directing a train to a station, he saw a young man in distress at the edge of the platform. He recognized his son Hugo, just before he fell into the tracks and died in the hospital. Leo, who hasn't seen his son for years, will find that he is involved in a bloody robbery. Leo will be closely watched by the police while tracking down his son's murderer, and at the same time, he will be under investigation. They will soon discover that Leo's skills in tracking and arresting violent criminals are not just the skills of subway drivers.