Little more than a week after the Twin Towers fell, this image began arriving in inboxes everywhere, attached to a forwarded email claiming it was the "last tourist photo" ever taken atop the World Trade Center. The man in the picture looked like a real tourist, all right, but nothing else about the scenario added up: his expression was too oblivious, the photographer's hand too steady, the timing of the snapshot too serendipitous to be true.


