The Sign of Four is a work in the Sherlock Holmes collection by Sir Arthur Conan Doyle. There are several main characters who are mentioned in the text.
Sherlock Holmes: Holmes is the detective extraordinaire who uses pure logic and his knowledge of human nature to quickly and effectively deduce the sequence of events that led to a situation occurring, in the case of the novel, that led to Mary's father disappearing ten years prior.
John Watson: Watson is Holmes's partner, a former member of the military and now a physician. His medical knowledge is frequently prevailed upon to aid these cases. He falls in love with Mary Morstan in the story.
Mary Morstan: An attractive socialite woman who's father had gone missing years earlier. She is being courted by another man, Thaddeus Sholto, but she is infatuated with Dr. Watson.
Major Sholto: A military major who worked with Morstan's father prior to his disappearance. He is the possessor of the jewels over which Mary's father was murdered, and revealed the murder to the other characters as they simply believed that he had disappeared.
Sholto Brothers: Dr. Thaddeus and Bartholomew are the sons of Major Sholto. Thaddeus is in love with Mary Morstand and attempts to woo her by frequently sending her pearls from his own collection. The two brothers attempt to find their father's cache of hidden jewels after Major Sholto dies mysteriously. Bartholomew finds the location of the treasure chest eventually—their father's attic—but he is also mysteriously killed.
Jonathan Small: Small was one of the original discoverers of the jewels in India. During an imprisonment he had informed the Major and Morstan of the jewels and sought to reclaim them after his release. He is one of the "Four" from whence the title of the story comes, who had discovered the jewels, and he and the other remaining member attempt to get the jewels back by whatever means necessary.
Sherlock Holmes, the famous detective known for his powers of observation and deduction.
Dr. John Watson
Dr. John Watson, Holmes’s friend and assistant. In this story, he is attracted to Mary Morstan, proposes to her, and is accepted.
Mary Morstan, Holmes’s client. She is a young Englishwoman whose father, an officer with an Indian regiment, failed to meet her, as he had sent word he would, at a London hotel. Her father has been missing for ten years.
(The entire section is 628 words.)