After rescuing a young boy named Leo from a brutal gang, the noble outlaw Za la Mort discovers the child is the heir to a massive fortune. He and his loyal partner Za la Vie must protect Leo from the Grey Rats, a ruthless criminal syndicate led by the villainous Grigione who are desperate to steal the inheritance. The chase leads them through the Parisian underworld and across the globe to secure Leo's safety and the secret of his past.