
(image from here)
"It's psychology that interests you, isn't it? Well, that doesn't change with time. The tangible things are gone—the cigarette end and the footprints and the bent blades of grass. You can't look for those any more. But you can go over all the facts of the case, and perhaps talk to the people who were there at the time—they're all alive still—and then—and then, as you said just now, you can lie back in your chair and think. And...