A Study in Scarlet.

Dr. Watson returns from Afghanistan with a wound and few prospects. He seeks someone to share lodging costs in London. An old friend introduces him to Sherlock Holmes. The two men take rooms together on Baker Street. Holmes makes a living as a consulting detective. He examines details others overlook. When a man is found dead in a vacant house, the police find no clear motive or suspect. Holmes agrees to look into the matter. Watson observes and notes what happens.