Did anyone NOT figure it out?
She says to him that the symptoms of the morphine overdose would be apparent by 5 mins and the guy explicitly says later on that it has already been 6 minutes, he was showing none of the symptoms. That part was obvious.
But, the moment Hugh(Ransom) says that he was a research assistant for Harlon everything fit together about who switched the medicine.
Although, I thought that Ransom himself forged the blackmail letter in order to make Marta confess and then burned the hospital to destroy the evidence clearing Marta. I didn't recognize the clues that Fran did anything.