LONDON — Don’t you just love a good murder?

Fictional, I mean. Curling up with a whodunit is one of my simple pleasures, and I’m fascinated by the people who make their living writing mysteries. I was fortunate to have interviewed P.D James back in the late ’70s, and I’ll always remember the way other diners leaned in when she started talking animatedly about planning a killing.

So, when I learned our London hotel, the Arch, was just a stone’s throw from the fictional home of Sherlock Holmes, a theme for our 30-hour London trip took shape.

The London stop was an add on the way home from a wonderful but exhausting trip to Edinburgh, Scotland, so we figured we deserved a quick posh stop. The Arch is such a place, situated on Great Cumberland Place, a street mentioned in a mystery I’d recently read, Anne Perry’s “Midnight at Marble Arch,” which really has nothing to do with Marble Arch. But a good title’s a good title, and a good hotel room’s a good hotel room. The Arch makes you feel as though you’re staying in a Marylebone townhouse, which you are. The hotel is a combination of several buildings on Great Cumberland, including one in which Winston Churchill briefly resided.

Its restaurant, Hunter 486, is named for a 1950s Marylebone dialing code (there’s one mystery solved) and features gems such as stone bass bathed in lemon grass-ginger broth. Our suite was below ground, so we were surprised to find a lovely outdoor sitting alcove perfect for plotting the day’s pursuits.

Plot and pursue we did, walking north about 10 minutes to the Sherlock Holmes Museum, located at the fictional 221b Baker Street home base of the fictional detective. So, here’s your decision: Do you fork over 15 pounds to stand in a block-long line for the eventual thrill of seeing the fictional home of a fictional detective? I mean, it’s put together with period furnishings to offer the feel of the detective, but it’s not as though Benedict Cumberbatch might stroll into the room. So the price does seem steep.

Side note: My husband did see Moriarty — or, rather, the fine actor Andrew Scott, who plays him in the BBC series — in “Hamlet” at the Almeida Theatre. It just closed, but it has been filmed for a TV run next year; watch your PBS stations.

You can buy an actual deerstalker hat in the Sherlock Holmes Museum gift shop, like the one the fictional detective wears. You can also pick up a Sherlock lunchbox. Huh. Wasn’t aware he ever carried a lunchbox. We opted out of the souvenirs, walking down the block to the Baker Street tube station in search of our next fictional detective home.

Alas, poor Hercule Poirot. The location for Whitehaven Mansions, his ›ictional apartment in the BBC series “Poirot” based on Agatha Christie’s novels and starring the wonderful David Suchet, was Florin Court, a 1936 art deco building on Chart-house Square near Barbicon tube station. The nine-story building looks drab and in need of a scrubdown, and whatever its residents are doing to their blinds, they need to stop.

As exacting as he is, Poirot will surely wish to move for any future episodes. As you might have heard, Kenneth Branagh will direct and play Poirot in “Murder on the Orient Express,” expected to be released in November. Don’t expect Florin Court to play a role.

Finally, time to pay homage to a real author. We stopped by the memorial to Christie, which mentions that her books have sold 2 billion copies (probably more by the time you read this) and touts the success of “The Mousetrap,” her whodunit that has played for 64 years, with no signs of closing, at St. Martin’s Theatre. I do suggest you see this one. Everyone has to, at least once. St. Martin’s is an intimate theater with an especially sweet bar.

Back to the Arch we go to discuss our perambulations in the hotel’s Martini Library, a contemporary yet snug living room where you can order up a cocktail and solve crimes or just curl up with your mystery. And keep an eye on the window. It overlooks Madonna’s apartment. Maybe you’ll spy her.