The Sherlock Holmes stories by Sir Arthur Conan Doyle made the London address 221B Baker Street famous all around the world. Doyle died more than 80 years ago, but his famous detective continues to receive fan mail and letters asking him for help. It's those missives that author Michael Robertson uses as a launching pad for his Baker Street Letters series of thrillers. The second in the series, The Brothers of Baker Street was recently released, and Robertson is in town today to discuss and sign the new title.

"One of the things that distinguishes [this series] from some of the other pastiches," Robertson tells Art Attack, "is that it's not really about Sherlock Holmes, it is about the Sherlock Holmes letters. I shamelessly use Sherlock as a hook, but the story is really about the letters and the phenomena around those."

Robertson says he's been a Sherlock Holmes fan from a young age; he read the novels as a kid and later watched the movies starring Basil Rathbone as the British detective on television. Thirty years ago he was taking a writing class and had a deadline looming, but he still had no idea for a story. That's when he saw a newspaper article about letters that were being sent to Sherlock Holmes at 221B Baker Street in London. "I thought, 'That's a gift from God.' It was the best idea anybody could have been given."

To his surprise no one else had written anything based on the situation, so he developed a screenplay centered on the letters. That story was a farce and included a character that wanted to be Sherlock Holmes who used the letters as a way to play out his fantasy. Robertson shopped it around for several years in Hollywood with no takers.

He came back to the idea a few years ago and decided the story was more suited to being a series of novels rather than a movie. "That changed everything. There are things you can get away with in a screenplay that you can't get away with in a novel so that changed the focus of it."

In the Baker Street Letters books, two brothers, Reggie and Nigel Heath, move their law offices into 221B Baker Street. As part of their lease, the two must reply to all the letters that arrive addressed to Sherlock. Being naturally nosey with a tendency to want to help people, Reggie not only responds with the required form letter, he also takes a personal interest in a few of the more compelling ones.

According to Robertson, one of the most difficult problems in writing the books has been creating believable characters that would write to Sherlock Holmes. "Much of the action in the novels is driven by who would write a letter and why and how can I force my character to respond?" Robertson says. "Once I had that figured out, the characters and the plot veer away from the Sherlock Holmes stories completely."

Robertson started his research with the letters themselves. In the mid-1980s, a set of the letters was published. He studied it very carefully and decided that the writers fell into three camps. First, there were the people who didn't have a good grip on fiction versus reality, especially people who were new to Doyle's novels.

Second, there were lots of children who wrote to him. The children would write in about a missing relative or other real world problems that the adults around them had apparently failed to help them with.

And then there are people who are writing for fun. Once it became known that the corporation located at 221B Baker Street would send a reply to any letter they received that was addressed to Sherlock Holmes, contemporary fans sent off hundreds of requests (apparently, having a reply on behalf of Sherlock Holmes was the closest thing to having one from the master detective himself, a sort of collector's item).

Robertson discarded the fans who were writing for fun, and, at least in The Brothers of Baker Street, has also stayed away from people who didn't understand the difference between fiction and fantasy. For his second title, he used a letter from a child as a starting point.

He also refamiliarized himself with Doyle's writings about Sherlock Holmes and did a fair amount of research on the London locations he used in the book. "You can't write a novel about Baker Street and not be aware of the history there," says Robertson.

In the first novel, one of the characters owns a St. Bernard. Realizing that some readers would assume a parallel between that large dog and the hound of the Baskervilles, Robertson inserted a bit of dialogue early in the action that would make it clear there was no connection between the two.

"I keep in mind everything I know about the canon while I write my books, but I'm not deliberately echoing Sherlock Holmes stories."

Robertson made several trips to London to visit the locations he mentioned in the books, including the modern corporate structure that stood at 221 Baker Street (at the time, it was the corporate headquarters for a bank which in fact received the real letters). Now the building containing 221B Baker Street is gone, so he feels less constrained by the physicality of the structure.

In some ways, Robertson is as mysterious as Sherlock's enemies. His bio on the book jacket says only that he works for an American corporation and does not include a photo. "It's not a publicity gimmick. I have a day job and I often go to England as part of my work. I think my colleagues there would clam up if they knew I was writing these books."

That's likely true. Many Brits are protective of the most famous fictional character to call London home. And then there's the fact that they don't know that he uses the British phrases he hears during teleconferences and trips to pepper his characters' dialogue. One of the phrases he heard recently was, "Let's not sacrifice our chickens out of order," meaning get your priorities straight. The phrase made it into the second book. "If they knew I was writing these books, my co-workers might start looking to see if I quoted them in the novels. Or worse, they might clam up."

Michael Robertson appears at Murder by the Book today at 6:30 p.m. For information, visit www.murderbooks.com or call 713-524-8597. Free.