Explain this Benjamin Button plot line, please?

I feel a little dumb asking this, but my excuses are a) I wasn’t quite in a movie-watching frame when we got there, b) about 4,237 people entered the theatre after the movie started, and they all sat down right in front of us, and c) my companion didn’t get it either.

So anyway…

What was the deal with the clockmaker? I understand the obvious metaphor at the end of the movie, but other than that, why was his story included? It seemed to have nothing to do with the rest of the plot.

Quick breakdown of my understanding: Blind clockmaker has a son. The son goes off to war and gets killed. Clockmaker makes a big clock that runs backwards, in some odd attempt to bring back the dead.

It didn’t have much to do with the plot, but it pretty much summed up the entire theme all in one fell (backwards) swoop.