One of the Lives Summary
The speaker imagines all the things (important and trivial) that had to fall into place in order for him to end up where he is now—sick, lying on a cot in some farmhouse somewhere. Sounds like a blast. He starts with events that don't seem to have too much of a direct impact on him—a friend whose dad died in the war, the dad's friend's older brother (if you can even follow that), and his kids.
Then he narrows in on more personally significant details. He talks about his choice of a college and about the events that led to his mother and father meeting. Finally, we find our speaker in a country house being attended to by a doctor. The poem ends with the speaker gazing out the window at the distant mountains and listening to plums drop from their trees.