Yet it’s hard to come away from the stories of 9/11 with a sense of anything other than an appreciation for the role randomness plays in our daily existence. There but for the grace of God, go I, as the 16th-century clergyman John Bradford is said to have phrased it—and how it can change the course of history.

The night before, the New York Giants game, in Denver, had gone late into the night, which meant that a whole host of New Yorkers showed up slightly late to work that morning, missing that final elevator up to the top of the North or South Tower; others survived because Roger Clemens was supposed to have been pitching for his 20th win at home with the Yankees on the 10th. The game was rained out, but not before people like Roy Bell, who worked on the 102nd floor of the North Tower, had rescheduled his 8 a.m. client meeting for 8:45 a.m. instead. Michael Lomonaco, the chef at the Windows of the World restaurant, would have normally been at work by 8:30, but he stopped to get new eyeglasses in the shopping concourse under the World Trade Center; he survived, while 72 of his coworkers were killed.

Jared Kotz, another attendee at that conference atop Windows on the World survived because a single publication was missing from his employee’s booth, so he offered to return to the office to fetch it. “I bid farewell to everyone and thought I would see them in an hour or less. I headed down the elevator,” he said later. “I walked into the office and called my London colleagues to let them know that everything but one box had arrived. I could see the time was 8:46. I remember thinking, Gee, I have plenty of time to get back downtown before the event starts. I was talking to one of my colleagues in London when I heard the plane go over.”