I would suggest watching the first episode of the series. It explains what is going on with the characters. You'll find out why Watson's head is on an android body and all about what happened to Holmes himself. I was confused at first also, but the first episode cleared it up. The main thing I noted was the fact that they use the titles of the original stories and then update them for the time period they take place in. You may understand what's going on better if you read Doyle's original stories. Read a Complete Sherlock Holmes if you can find it. They also have The Adventures of Sherlock Holmes as a separate volume. There may also be other volumes. Ask at a library for Sir Arthur Conan Doyle or Sherlock Holmes and they can direct you to the Call Number. If you want to buy a book, look under Mystery in the book store. Waldenbooks has a good selection. Good luck!
Review of Sherlock Holmes in the 22nd Century
