What is the core of a Sherlock Holmes story?

Now that I've written a book of Sherlock Holmes stories, I feel (no doubt, wrongly) that I can pontificate on what the key is.

I think it is all about finding a "hook." Something that the whole story hangs on or is built around.

If you look at the original short stories they all have some kind of hook, no matter how seemingly insignifcant, that they pivot round. In "The Red-Headed League" it was the relative rarity of red hair. In "The Copper Beeches" it was short, chestnut hair (oh, hair again). "The Cardboard Box" hung on two people having a similar name.

Go through them all and you will find something.

I used this model in TFMSH. "The Drury Lane Pawnbroker" hung on how long Pawnbrokers were required to keep items. "The Naval Architect" hung on how trains would be held close together at certain stations. "The Brandon Park Bench" was built on lipreading.

If you can find a seemingly rare fact, it is possible to build a story around it and I feel that is what Arthur Conan Doyle did a lot of the time.

Go on. Have a re-read and pick out what you think each story is built around.