Complex sentence: Frank and Cora eventually patch together their relationship and plan for a future together, but as they seem to be prepared to live "happily ever after", Cora dies in a car accident while Frank is driving.
Split into simpler sentences: Frank and Cora eventually patch together their relationship and plan for a future together. But as they seem to be prepared to live "happily ever after", Cora dies in a car accident while Frank is driving.