Well, in a nutshell it is a 4 hour saga about the Luchiano crime family in Sicily. But, I'll go into a little more detail.

At the beginning of the movie, the Don's son(Michael interestingly enough)is killed by one of his rivals. Don Luchiano and his other 3 sons then swear revenge on the man not matter what. About 10 years later, the Don and his sons are all murdered, nevering getting their vengeance on Michael's killer. So Don Luchiano's widow and daughters-in-law now make the pact that they will get revenge on the killer of Michael and the other Luchianos who had been killed.

Thats all I can tell you. I hope I haven't given away too much already. It's not one of the greatest movies ever made, I'll admit, but its worth checking out if you have some time on your hands. I'd rate it 2 stars out of 4.