Mystery Trivia Tuesday: Sherlock Holmes

After an absence of almost 10 years, Conan Doyle brought Holmes back for 34 more adventures. This quiz contains questions about Holmes great hiatus and his return to London.
1. What did Dr. Watson do when he first saw Holmes after presuming he was dead?
2.  Where did Holmes spend his time during his absence?
3.  Who was the only person to know that Holmes was still alive?
4. What alias did Holmes use?
5. Why did Holmes return to London?