First the 1990s, after the retired government worker from Memphis, Tenn., got serious about travel. Wheeler and his wife became so intimately acquainted with London theater and shopping that he began writing guidebooks and operating tours of the city and the nearby English countryside.

Then the 1890s: A childhood interest in Arthur Conan Doyle's Sherlock Holmes novels and stories never abated, and Wheeler amassed a detailed knowledge of the legendary Victorian detective.

Wheeler cross-bred his files to create a guidebook on Sherlock's world, and an updated version, "The New 'Finding Sherlock's London'" (iUniverse, $22.95) has just been published. It lists more than 300 sites.

Most of us have less of an addiction to the master detective and his friend, Dr. Watson ... but an attraction nonetheless. Amazon.com remains fully stocked with the original Sherlock titles and hundreds of spinoffs, knockoffs and rip-offs. Countless films have been made of the investigative duo, and a new, big-budget "Sherlock Holmes" starring Robert Downey Jr. is being readied for Christmas release.

A great deal of its filming this past winter was done in London -- an elementary decision, as so many cases were set there, and the metropolis retains something of the feel of crimes and clues tucked into waistcoats and fog-darkened shadows.

Going to London soon? We recently interrogated Wheeler, who offers these slice-of-Sherlock tips.

The absolute must-see

The famous apartment Sherlock and Watson shared at 221-B Baker St. never existed, but Baker Street is still the best place to start, according to Wheeler.

"The Sherlock Holmes Museum, on the 200 block of Baker Street, has a sign over the door that reads 221-B. But it's not really where the fictional place would've been, and the museum's actual address is 239. But the museum has a replica of Holmes and Watson's rooms on the second floor. The ground floor has a kind of curio shop where you can buy Sherlock Holmes items.

"Across from the museum at the Baker Street Underground station is a statue of the detective.

"Where did Holmes actually live? In my book, I consider it 31 Baker St. I came to that conclusion studying 'The Adventure of the Empty House,' in which a route is given that ends up at an empty house across from their rooms."

--Best place to buy a deerstalker hat and a calabash pipe

Wheeler: "Probably the museum, where the hats go for about 20 ($29). The shop also has books and everything else for sale.

"On Oxford Street is a tobacco shop that has been in business a long time. It might be where Sherlock bought his pipe tobacco or cigarettes. He had cigarettes in some of the stories."

Best Sherlockian place to eat

"Go to the Sherlock Holmes Pub, at 10 Northumberland St. Its second floor has a restaurant with decent pub food -- bangers and mash (sausages and mashed potatoes). And behind glass is a replica of the 221-B drawing room, just as you imagined it. There's good beer downstairs.

"Restaurants mentioned in the Sherlock Holmes adventures that are still in business include Simpson's-in-the-Strand, at 100 Strand -- mentioned in 'The Adventure of the Dying Detective' and 'The Adventure of the Illustrious Client.' If you order the tableside carved roast at Simpson's, remember to tip the carver in cash. And there's the Criterion Grill, 224 Piccadilly, where Watson first heard of Holmes, in 'A Study in Scarlet.' At the Criterion, ask if they still have the good value pre-theater dinner."

Best place for Sherlock sleep

You can stay at several hotels mentioned in the stories, according to Wheeler.

"There's The Charing Cross Hotel, which I like because it's at the center of Sherlock's London. It's within walking distance of the Simpson's-in-the-Strand -- Sherlock's favorite restaurant. And Trafalgar Square is right across the street. The Charing Cross is a nice hotel and was recently refurbished. Also, the Charing Cross Hotel was mentioned in 'The Adventure of the Bruce-Partington Plan.'

"At Brook and Davies streets is Claridge's. It's mentioned in several stories and is probably the only hotel in which Sherlock stayed as a guest. After he retired and moved to the Sussex countryside to become a beekeeper, he returned to London in 'His Last Bow' during World War I as a double agent feeding false information to the Germans. In the story, he was staying at Claridge's. It's a five-star place (www.claridges.co.uk).

"Others include The Grosvenor Hotel, on Buckingham Palace Road (www.grosvenor-hotel-london.co.uk) -- mentioned in 'The Final Problem' -- and The Langham Hotel (http:// london.langhamhotels.co.uk/en), on Portland Place: 'The Sign of Four,' 'A Scandal in Bohemia' and 'The Disappearance of Lady Frances Carfax.'

"My favorite, though, is The Royal Horseguards. You know you're in London when you stay there (www.theroyalhorseguards.co.uk). It's a great old hotel within a half-block of the Sherlock Holmes Pub. It's also near the Embankment tube station, which has four underground lines. You can get anywhere quickly from there. The tube station is where London Walks offers its Holmes tour, Fridays at 2 p.m., for 7 ($10.19) per person. Reservations aren't required; just show up (www.walks.com)."

The 'hood that looks most like Sherlock's turf

"I'd say Craven Street, off Northumberland. It's where a lot of houses were never torn down, and many are Victorian. It's one of those backstreets just east of the Sherlock Holmes Pub. This area is covered in the London Walks tour."

Best short walk for casual fans

"One I cover in my book is only six-tenths of a mile and retraces the route to 221-B Baker St., as covered in 'The Adventure of the Empty House.' The walk starts at Cavendish Square and ends up on Baker Street at the true Holmes-Watson site. The buildings on the walk are a mix of commercial and residential. Probably more commercial these days: It's expensive to have a home in London.

"This is in a part of London right off Oxford Street which has big stores -- but you're taking backstreets. The route is flat; this is an easy walk."

Best add-on -- for mood

"Dennis Severs' House, 18 Folgate St., in Spitalfields, is a must for seeing how Londoners lived in the 19th century. Their Monday evening tour is the most unique. Advance booking is necessary, and the cost is 12 ($17.46) per person. They also offer daylight tours of the house most Sundays between noon and 4 p.m. (8 per person), and between noon and 2 p.m. the Monday following the first and third Sundays (5/$7.28 per person). No advance booking is required for the daylight tours (www.dennissevershouse.co.uk)."

IF YOU GO:

The Sherlock Holmes Museum, 239 Baker St., London, is open 9:30 a.m.-6 p.m. daily. Admission: 6 ($8.72); 4 ($5.83) for 15 and younger. Details: www.sherlock-holmes.co.uk

SERIOUS FAN, EXHAUSTIVE BOOK

Thomas Wheeler, 78, is a member of the Sherlock Holmes Society of London, one of the foremost associations of serious fans. In Memphis, Tenn., he is also a former First Garrideb of the Giant Rat of Sumatra organization.

(Sherlock clubs tend to acquire odd names based on Arthur Conan Doyle's writings. A giant rat of Sumatra was mentioned in the story "The Adventure of the Sussex Vampire." The Memphis president is similarly and obscurely titled to honor "The Adventure of the Three Garridebs.")

Die-hard fans are indeed a serious bunch, and "The New 'Finding Sherlock's London'" is guilty as charged. It could easily be stocked in a bookstore's travel aisle -- or among reference guides in the mystery area. The 300-some pages list more than 300 spots from one end of London to the other.

The volume is organized in several ways. One is by story/novel according to the year in which each was set. (Got a favorite? Just look it up: Review the synopsis and literally view the scenes.) Another section groups sites by which of 80 Underground stations they're near -- a boon for time-crunched visitors to whom Holmes-Watson sites may be an easy by-the-way stop. Other groupings are by train stations and 10 London rail lines. Five walking tours are outlined, and two lists in the back tell which adventures feature 450 named characters.

The book is exhaustive, but it makes it infinitely easier for fans to find what they seek in London. As the man with the magnifying glass noted in "A Case of Identity" (1891), "The little things are infinitely the most important."