Passenger to Frankfurt - Agatha Christie

Oh, come on, Dame Agatha. You´ve got be kidding me:

 

A mentally insane Hitler doppelgänger died in the bunker, the real Hitler went to the Argentine and fathered a child. Uh, uh, let me guess: Franz Joseph.

 

And this whole swapping situation at the mental institution.

 

 

[Source]

(show spoiler)

 

And soon as you think, it can get worse than the stuff that has happened before, you´ve got proven that you are wrong.