private eye

a person not on the police force who investigates criminal or illicit activity or searches for missing persons unable to get the interest of the police, they hired a private eye to find their missing daughter Synonyms dick, gumshoe, hawkshaw, investigator, operative, private detective, detective, private investigator, shamus [slang], sherlock, sleuth, sleuthhoundRelated Words shadow, tail, tracer, tracker; fed, Federal, G-man, narc (or nark) [slang], plainclothesman