About what?
About the past, which was so near and so short.
They were leaving their paradise of childhood and ignorance.

They spoke of a house and a garden where they had both lived.
The house absorbed them.

It was surrounded by a garden wall, so that from the road all you could see was the tip of the eaves, and you couldn't tell what was going on inside of it.
They prattled: "The rooms, when we were little and they were so big--" "It was easier to walk there than anywhere else." To hear the children talk, you would have thought there was something benevolent and invisible, something like the good God of the past, behind those walls.

She hummed an air she had heard there, and said that music was easier to remember than people.

They dropped back into the past easily and naturally.