S.J. Rozan loves William Blake. The epigraph to her Shamus Award—winning mystery Winter andNight quotes these lines from Songs of Experience: "Then come home my children/ The Sun has gone down..." The indelible shadow of 9/11 had yet to darken the skies when she chose those words. But in its aftermath, when it became time for her next book, she realized that it could not be another installment in the acclaimed Lydia Chin/Bill Smith series. "At first, like everyone else, I could not write at all," she says. "Then I realized that I couldn't write about anything but 9/11. But to put that event in the context of my series would trivialize it."

The result, her haunting tribute to that time and place, is her first stand-alone thriller, Absent Friends, out from Delacorte this month. The story concerns a legendary firefighter who dies a hero's death in the towers, and the posthumous revelations about his life that come as aftershocks to the close circle of his friends from his youth in Staten Island. The novel showcases Rozan's admirable literary style: her supple command of plot; fast-paced, witty dialogue; and concern for social and moral issues.

The book also establishes a first for this type of novel, an epilogue titled "Explanation." This section consists of anecdotes, observations and poems that provide clues to the 18 recurring chapter headings that mystify the reader as the narrative unfolds. That part of the book actually came first, Rozan says. As she prepared to write, fragments of impressions related to 9/11 began to inhabit her imagination. "I interviewed a tremendous number of people about that day. Some of these anecdotes came from them. Some happened to me. I hope you can't actually tell which is which. They're all true," she says. When she determined to use four narrative voices, it occurred to her that each voice could be identified by chapter headings. Thus such headings as "Secrets No One Knew'' and "The Man Who Sat by the Door" and "The Way Home" are repeated throughout the book. She was prepared for an editor to argue about this idiosyncratic device, Rozan says. "But Kate Miciak knew right away what I was trying to do."

Multiple voices is one of the major differences between her mysteries and AbsentFriends. The mysteries are all related from the point of view of either Lydia Chin or Bill Smith. In contrast, the four points of view in Absent Friends allow the reader to know more than any individual narrator.

How does a successful architect, which Rozan was for more than a decade until she left her firm this past June, segue into writing mysteries and thrillers? Not at all strange, Rozan says. Growing up in the Bronx, she always wanted to be a writer. She knew her genre would be crime fiction because she was fascinated by the classic voice of the tarnished hero, a distant observer who becomes involved in other people's lives.

But first she took a detour. Having become convinced while in college hat "you can't just be a writer; you need a profession" (a theory she now recognizes as false), she went to architecture school and thereafter thoroughly enjoyed her métier. She describes herself as "a construction guy" who went out in the field, went up on the scaffold and became "telephone central" as she administered a project. "The job was so good that when I found I wasn't happy, I knew it wasn't that." She took a course in fiction writing and started a novel that seemed to have no ending. So she wrote a short story and was astonished when it was immediately published in PI Magazine. Encouraged, she signed with agent Steve Axelrod, and continued writing.

Soon she had three unsold books. But Axelrod believed in her, she says, and when he finally connected with St. Martin's in 1994, she felt validated. A steady stream of prestigious nominations and prizes for her mystery series (eight books so far) followed. When she won the Shamus for Concourse, she found herself getting up in the middle of the night to see if it was still there. After she also received the Edgar for Winter and Night, she finally accepted that she could afford to quit her day job. She lives modestly in Greenwich Village, where she shares her apartment with a grumpy cat.

Wry humor and city smarts distinguish Rozan as well as her characters, as PW discovers when we meet at a tea emporium in Manhattan. Petite but not fragile, she gives the impression of being well-grounded in her life and her career. Her hair, dark with gray strands, is tucked neatly behind her ears. Her face and manner are far more warm and animated than her jacket photo would suggest.

It's clear that her desire to write about social issues is one of Rozan's driving motivations. The central theme of Absent Friends is whether getting at the truth is always a good thing, and whether one person's conceptions of morality and justice may carry their own unusual validity. Do the revelations about firefighter James McCaffery's past moral misdeed cancel his bravery in the World Trade Center? How many good deeds it takes to overcome bad deeds is an unsolvable enigma, Rozan muses. "I hope the book helps people open their hearts to the idea that these are questions that have to be continually asked but not answered."

Another mystery remains. Why the initials S.J. rather than her given name? Not at all mysterious, Rozan declares. Her given name (Shira) is biblical and unfamiliar. People tended not to hear it correctly and to return calls to "Roseanne." When she decided to write books, she solved that problem by establishing a new ID. It's a signal instance of Rozan's rational, controlled approach to life, which, she would be the first to say, cannot be controlled.