“Through the grace of the people in my life, I am able to conduct what appears at first glance in many ways more normal than it is beneath the surface,” Mrs. Manning said recently. “My husband, he’s been my hands.”

There is no clear accounting of how many people were seriously injured that day. Of the $7 billion distributed by the federal government’s September 11th Victim Compensation Fund, $6 billion went to the families of those killed at the World Trade Center, at the Pentagon, and in the plane that went down in Pennsylvania; $1 billion went to the injured. Most of the injured were firefighters, and most of the payments were for respiratory ailments.

Burns accounted for 40 of the 2,680 injury payments.

Eighteen of the most gravely burned were taken that day to NewYork-Presbyterian Hospital. A dozen of those survived.

Some, like Mrs. Manning and Harry Waizer, who both worked at Cantor Fitzgerald, have regained a sense of equilibrium. For others, like Elaine Duch, who was a senior administrative assistant in the real estate department at the Port Authority of New York and New Jersey, the before and after are clearly demarcated.

Ms. Duch, 56, has cut herself off from her old friends, partly because, as she put it, “I’m never going to be the Elaine that I used to be.” Of her current friends, Ms. Duch said, “Well, see, they did not know me before, they only know me as an injured person.”

Nowadays, she goes to the New Jersey Shore with her twin sister and a woman who saw her on the news and who sent her cards and letters every day of the five months she spent in rehabilitation. She no longer drives because her hands are too weak and she is easily rattled. She avoids zippers, tiny buttons and opening the wax paper in cereal boxes. She suffers through summers and winters because her burned skin does not tolerate heat and cold very well.

Image BY HER SIDE Lauren Manning with her husband, Greg, make for a different picture this month, than they did in the first few months after the attacks. I am able to conduct what appears at first glance in many ways more normal than it is beneath the surface, says Mrs. Manning, 47. Credit... James Estrin/The New York Times

“I felt like I was young when this happened, and I feel like I’m old now,” Ms. Duch said. “I feel like my past life was a different life.”