sherlock

a person not on the police force who investigates criminal or illicit activity or searches for missing persons one of literature's most eccentric sherlocks, Nero Wolfe manages to solve mysteries without so much as leaving the confines of his own home Synonyms dick, gumshoe, hawkshaw, investigator, operative, private detective, private eye, private investigator, shamus [slang], detective, sleuth, sleuthhoundRelated Words shadow, tail, tracer, tracker; fed, Federal, G-man, narc (or nark) [slang], plainclothesman