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WilliamPurry
Since: Apr, 2019
Chabal2
Since: Jan, 2010

I think it's a Miss Marple or at least Agatha Christie story where the director of an orphanage/a mental institution is secretly using his charges to commit crimes to keep his place funded.
One of the people involved suffered from a delusion that his father was a famous person such as Winston Churchill, but turned out to be the director.