Mr. Young from Property Management sends a message: 'Which residents aren't going home? Send your apartment number for a gift.' Resident 503 private messages: 'Don't send it. He's a killer.' In a university dorm, the Dorm Supervisor sends: 'Surprise inspection. Turn on your lights.' Student 503 private messages: 'Don't turn on the lights. He's a killer.' The same '503' warns about officials luring out the living. Is '503' a savior or a hunter?