Maybe It Is a Game for Knights:
Chess-Playing Eyes
Ever since Philip Marlowe set up his board to work out a problem or two, chess (and its connection with knights, and all that suggests) has become a sort of recurring code word in private eye fiction.

• Philip Marlowe by Raymond Chandler
  
  
• Mitch Roberts by Gaylord Dold
  
  
• Harry Moseby by Alan Sharp
  
  
• Paladin by Sam Rolfe and Herb Meadows
  Have Gun, Will Travel's Paladin wasn't content to merely play chess; he named himself after a chesspiece, and left it as a calling card of sorts.