Why did holmes want to look at the hotel register, and what did he find?

Holmes wanted to look at the hotel register to make sure if the man was staying at their hotel. He came to know that he was not.  There were other people staying there.
Sir Arthur Conan Doyle wrote "The Hound of the Baskervilles" which is a crime novel and the main character in the novel is the famous detective Sherlock Holmes.