"The entire crime-fighting fraternity yesterday bade a tearful farewell to the last 'locked room' mystery at a large banquet held in its honor. The much-loved conceptual chestnut of mystery fiction for over a century had been unwell for many years and was finally discovered dead at 3:15 A.M. last Tuesday."
Then it turns out that the locked room mystery was murdered . . . in a locked room. — Source: TV TROPES ("Locked Room Mystery"). [Watch out for SPOILERS on this site.]
Category: Detective fiction