I think it should cover the 17? years (i think) from the end of the Godfather Pt3 to the death of Michael, with Vincent and such trying to cope with Mary's death/becoming Godfather
I hate people who are against vengance, they say that killing them won't make the lost come back, the way i see it, if you let them get away with that, they'll do it again and again until you are destroyed.
