Many question, not satisfied

Rating: 7/10 (16 February 2020)

It left me with many questions.
SPOILERS AHEAD!
Why Harlan seems to be the mastermind behind all of this (well, even behind faking his own death?
Why Ransom hired Benoit? It is obvious that the blood test can prove Marta guilties easily.
How did Benoit gets Mrs.Thormbey to talk?
Why Harlan told Ransom details of his will?
Why suddenly Benoit jumped into Marta while she's confesing?
Why Benoit does not seem to be a greate detective to me? Just nornal
Many more. I very much love these mystery movies. The story telling, acting is good, but it does not satisfy me as a murder mystery movie. Should have some deeper layers, a mastermind, or a better plot twist.