Hard-Boiled stories involve police or private investigator, villains, and a victim. One major distinction in hard-boiled fiction is the language.  Margaret Maron, James M. Reasoner, Raymond Chandler, Bill Pronzini, and other famous hard-boiled fiction writers use a different kind of language.  They call police officers or private investigators “dicks.”  There are also words like geezers.  A geezer means an older gentleman.