The first chapter of 'A Study in Scarlet' introduces Dr. John Watson, who returned to England after serving as an assistant surgeon during the Second Afghan War and suffering from a series of misfortunes. He meets Stamford, an acquaintance from medical school, who introduces him to the eccentric scientist Sherlock Holmes, leading to a proposed living arrangement. Holmes exhibits a remarkable enthusiasm for his scientific discoveries and a peculiar intuition, which piques Watson's interest.