S.O.X. Agent Knight.
An agent with the Secret Organization for Extermination, America's Top Underworld Crime League, known as "S.O.X.".
Agent Knight is sent by the organization's chief to make contact with another of their agents. However, it is Smart who inadvertently responds to the password and recruited as S.O.X.'s Assassin Number 1.
[Comic Strip Story #10 (Unofficial title: "Max in Sox").]