Related Clues:

• Gumshoe
• Private eye
• Investigator
• Shamus
• Sleuth, informally
• G-man
• P.I.
• Private eye, for short
• P.I., e.g.
• Detective
• Sleuth, for short
• Clue collector, slangily
• Old-time gumshoe
• Spade, for one
• Investigator, slangily