Apologies if this has been discussed before but I just thought of a question... Why wouldn't Michael take Pentangeli into strict confidence and let him in on the ultimate plan? Wasn't Frankie the most trusted Corleone Family member in New York at that time? I am interested to hear the main reason why? Michael's fear of plan leaking? Obviously at the top of the list but why else? Thanks.
Mark, if I understand your question correctly:
Michael had no need to tell Frankie about his Cuban plan with Roth (prior to the Tahoe shooting) because Frankie wasn't part of it.
He also didn't tell Frankie about his plan to kill Roth before the New Year because he hadn't thought that up until he got to Cuba, when he learned that Roth planned to kill him just after the New Year. So, when he told Frankie to just go along with him until he could find out who the traitor in his family was, he was telling Frankie about as much as he knew at the time.
Plus, as Oli said, Frankie wasn't the sharpest knife in the drawer, and Michael had no incentive to tell him any more than he needed to know to be helpful to Michael.
