The name Hieronymus is the Latin source of the name Jerome. By that measure, Detective Hieronymus Bosch should perhaps go by Jerry for short. But I went with Harry instead, choosing it as a nod to Dirty Harry Callahan and Harry Caul, two detectives from films that were important to me in my evolution as a storyteller. My hope is that Harry Bosch shares a kinship with those two Harrys, as well as with the characters created by the hugely influential writers listed as inspirations earlier.

With a name, a history, and a mission, Harry Bosch seemed to lack only a code. Every detective, private or public, in the annals of crime fiction has a personal code by which he or she makes a stand. Raymond Chandler wrote an essay about it: “Down these mean streets a man must go…”

I decided to keep it short. I wanted Bosch to have a code that would be telling of his status as someone who for much of his life was on the outside looking in. I wanted him to have a code that would not let him forget his origins and that would plant him firmly on the side of the underdog. I wanted Bosch to operate with a code of conduct and fairness that would not allow him to suffer fools lightly or leave him beholden to the powerful and rich. He would operate fairly and never use his position to his personal advantage. He would understand that he must give his best effort on each case no matter who the victim may be or where the clues may lead.

Everybody counts or nobody counts.

This would be his code.

The creative fulfillment that comes from writing a series of novels with a returning character is that the biography of that character continually evolves. The series moves forward at the same time it moves backward. New cases, new missions, carry the reader forward. But strewn throughout the stories are the glittering nuggets of history that take the reader into the past.

So, too, Harry Bosch evolves. The man built to be relentless and bulletproof now shows he is vulnerable. In recent years he has discovered a daughter, a piece of history that in many ways turns all that came before it upside down. Through her, Harry can be gotten to. It changes things, especially him.

Through fifteen novels I would say that Harry Bosch has mellowed. He is still an outsider with an insider’s job. He still won’t suffer fools lightly or accept bureaucracy when it gets between him and the completion of the mission. But he has a greater sense of himself and more knowledge of human nature. His mission has made him a man who is both hopeful and cynical. He knows what true justice is and has more insight into redemption. He has a better understanding of the frailties that lead to the many different kinds of human corruption.

In Angels Flight, the sixth book in the series, Harry opens a pack of matches and finds a fortune printed on the inside flap. It reads: Happy is the man who finds refuge in himself. For Bosch it is a hint of what is to come. Harry pursues his mission at the same time he seeks refuge and continues to find it in himself. That makes his a biography still in progress.

The house my father built on Highland Avenue may still be standing, but the tunnel is long gone. The day I escaped from the book tour and drove out there, it was the first thing I noticed. The sloping property had been resculpted in the years since my family left. The drainage gulley had been filled and the front lawn leveled. The woods that were across the street were gone as well, replaced by a well-manicured subdivision.

Maybe it’s true that you can’t go home again. But not finding the tunnel that day didn’t bother me. I was thankful for what it had given me. An early test of character and a memory that would live on in my imagination. If I am lucky, the character who came out of that tunnel will live just as long.

Born in Dublin, Ireland, in 1968, John Connolly received a BA in English from Trinity College in Dublin, then an MA in journalism from Dublin City University, taking a job as a freelance journalist for the Irish Times, which he did for five years; he continues to contribute articles from time to time. He has also worked as a bartender, a waiter, a government official, and at London ’s famous Harrod’s department store.

His first novel, Every Dead Thing (1999), introduced Charlie Parker, the dark ex-cop who has starred in most of his subsequent work. It achieved the virtually inconceivable double honor of winning a Shamus Award from the Private Eye Writers of America and being nominated for the Bram Stoker Award by the Horror Writers Association. Crossing genres in the same work of fiction has been historically both risky and difficult, but Connolly has managed it with a rare ability to plot brilliantly while writing original and distinguished prose.

In addition to the Charlie Parker books, Connolly has produced the stand-alone suspense novel Bad Men (2003); a collection of horror tales, Nocturnes (2004); and a noncrime novel, The Book of Lost Things (2006). One of the stories in Nocturnes, “The New Daughter,” serves as the partial basis for a forthcoming film with that title starring Kevin Costner and Ivana Baquero. His most recent books are The Gates, “a strange book for strange young people,” and The Lovers, a Charlie Parker novel.

John Connolly lives in Dublin and, sometimes, in Maine.

I never met Belinda Pereira. By the time I heard her name spoken for the first time, she was already dead. But on the night that she was killed, I stood outside her apartment in the rain, and I listened as a detective described the circumstances of her death. She was twenty-six years old. Were it not for her, I don’t think I would be writing the books I write. In a way, they are an attempt to make sense of her murder, and for that reason they all fail.

Because there was no sense to her murder.

Dublin is a peculiar city. It closes down for the Christmas season and doesn’t really find its stride again until early in the New Year. When I worked as a journalist, Christmas was a period during which most staff journalists preferred not to work. It wasn’t simply that they wanted to spend time with their families, as most people do at that time of year, or to leave the grim winter weather behind and head for somewhere warmer; it was because nothing much really happened in Ireland at Christmas. During the Troubles, even the terrorists would call a brief cease-fire beginning about December 24, so they could stay at home and pretend to be ordinary men and women without blood on their hands.

But I was a freelance journalist, and I worked whatever hours I was offered because I was afraid that if I turned them down, I would never be given work again. By 1996, I had essentially been a full-time freelancer for the Irish Times newspaper in Dublin for three years, and had graduated from education and assorted features to regular shifts in the newsroom, which was how I came to be working on December 28, when Belinda died.

One of the tasks newsroom journalists are required to do is to call the police or the fire department and ask if anything newsworthy has happened. These calls are usually made every hour because, personal sources apart, it is not the place of the police and the fire department to take the initiative in informing journalists of interesting events. In fact, the office of the Irish Times could have been on fire, and the fire department wouldn’t have called us to let us know. That was just the way things were.