There comes a time when the detective holds an audience with all relevant suspects in a room. All the major players.
And tells how skillfully the perpetrator fooled everyone. And how the detective fooled the perpetrator.
All mysteries solved. Right?
Well, all good mysteries end with another mystery, that turns the whole tale ass backwards. Makes it into an ourobouros. A snake eating its own tail.
Great mystery writers go for resonance and a cyclic nature of justice. Creates an even bigger mystery.
Oh well. I'll see if I can top even that.