Post Office Box 1001

A young man named Rafael is killed in the street opposite the Police Headquarters in Barcelona. Miguel and Marcial, of the Criminal Brigade, investigate the murder and are, in the room of the dead, a copy of "La Vanguardia". In the newspaper found indicated an announcement requesting a manager for a chemical company, through a strong bail, and with an indication of writing for more information to the Post 1001. With this discovery begin some difficult police inquiries that may lead to the arrest of the murderer.