Almost all of the Sherlock Holmes stories are told from the first person point of view with Dr. Watson as narrator.  Dr. Watson is Holmes’s roommate, friend, and assistant.

You can tell first person point of view by the use of pronouns.  You will see the pronouns I, me, we, and my.  These are first person pronouns.  Watson refers to himself.

We were seated at breakfast one morning, my wife and I, when the maid brought in a telegram.

Watson describes Holmes’s actions and repeats what he says, sometimes asking him to explain his reasoning.  However, Watson does not really ever know exactly what is going on.  This creates more suspense for the reader, because we have to guess and Watson withholds information.