A Study in Scarlet

=== Part I: The Reminiscences of Watson ===

In 1881, Doctor John Watson returns to London after serving in the Second Anglo-Afghan War and starts looking for a place to live. An old friend of his named Stamford tells him that Sherlock Holmes is looking for someone to split the rent at a flat at 221B Baker Street but cautions Watson about Holmes' eccentricities. Holmes and Watson meet and, after assessing each other and the rooms, they move in. Holmes is a "consulting detective", and his frequent guests are clients. After a demonstration of Holmes' deductive skills, Watson's disbelief turns into astonishment. A telegram requests a consultation in a murder case. Watson accompanies Holmes to the crime scene, an abandoned house on Brixton Road. Inspectors Gregson and Lestrade are already on the scene. The victim is Enoch Drebber of Cleveland, Ohio, and documents found on his person reveal that he has a secretary, Joseph Stangerson. The room is splashed in blood, and the word "RACHE" (German for "revenge") is written in it on one wall; however, Drebber's body shows no wounds. Dismissing the message as a ploy to mislead the police, Holmes deduces that Drebber was poisoned and supplies a description of the murderer. Upon moving Drebber's body, they discover a woman's gold wedding ring.
Holmes places notices in several newspapers about the ring and buys a facsimile of it, hoping to draw the murderer – who has apparently already tried to retrieve the ring – out of hiding. An old woman answers the advertisement, claiming that the ring belongs to her daughter. Holmes gives her the duplicate and follows her, but she evades him in a way that leads Holmes to believe that "she" was actually a young man in disguise, an accomplice to the murderer. A day later, Gregson visits Holmes and Watson, telling them that he has arrested a suspect. He went to Madame Charpentier's Boarding House where Drebber and Stangerson stayed before the murder. Drebber, a drunk, attempted to kiss Mrs. Charpentier's daughter, Alice, which caused their immediate eviction. He, however, came back later that night and attempted to grab Alice, prompting her older brother to attack him. He attempted to chase Drebber with a cudgel but claimed to have lost sight of him. Gregson has him in custody on this circumstantial evidence.
Stangerson is later found dead in his hotel room, stabbed through the heart and with the word "RACHE" written in blood on the wall. The only things Stangerson had with him were a novel, a pipe, a telegram saying "J.H. is in Europe", and a small box containing two pills. Holmes tests the pills on an old and sickly Scottish Terrier in residence at Baker Street. The first pill produces no evident effect, but the second kills the terrier. A young street urchin named Wiggins then arrives. He is the leader of the Baker Street Irregulars, a group of street children Holmes employs to help him occasionally. Wiggins has summoned a cab Holmes wanted. Holmes sends him down to fetch the cabby, claiming to need help with his luggage. When the cabby comes upstairs, Holmes handcuffs and restrains him. The captive cabby is Jefferson Hope, the murderer of Drebber and Stangerson.

Part II: "The Country of the Saints"

In Utah's Salt Lake Valley in 1847, John Ferrier and a little girl named Lucy, the only survivors of a small party of pioneers, are rescued from death by a party of Latter-day Saints led by Brigham Young, but only on the condition that they adopt and live under the Mormon faith. Years later in 1860, a now-grown Lucy befriends and falls in love with Jefferson Hope. However, Young forbids her from marrying outside the faith and demands that she marry either Joseph Stangerson or Enoch Drebber, both sons of members of the church's Council of Four. Ferrier, who has adopted Lucy and sworn never to marry his daughter to a Mormon, sends word to Hope in order to help them escape.
Lucy is given one month to choose between her suitors. Hope arrives on the eve of the last day, and they all escape under cover of darkness. While Hope is hunting in the mountains, the Mormons catch up to the escapees; Stangerson kills Ferrier, while Lucy is taken back to the Mormons' settlement and forced to marry Drebber. She dies of a broken heart less than a month later. Hope breaks into Drebber's house the night before Lucy's funeral to kiss her body and remove her wedding ring. He swears vengeance on Drebber and Stangerson but begins to suffer from an aortic aneurysm, causing him to leave the mountains to earn money and recuperate. After returning years later, he learns Drebber and Stangerson have fled Salt Lake City after a schism between the Mormons. Drebber is now wealthy from Lucy's estate and Stangerson has become his secretary. For over 20 years Hope pursues them; in Cleveland, Hope recognizes Drebber who has Hope imprisoned for a few months as a "rival in love". After being released, Hope tracks them to Europe through France, Russia, Denmark and to England.
In London, Hope becomes a cabby and eventually finds Drebber and Stangerson. After the altercation with Madame Charpentier's son, Drebber gets into Hope's cab and spends hours drinking. Hope then takes him to the house on Brixton Road and forces Drebber to recognize him and to choose between two pills, one of which is harmless and the other poison. Drebber takes the poisoned pill, and as he dies Hope shows him Lucy's wedding ring. The excitement coupled with his aneurysm causes his nose to bleed; he uses the blood to write "RACHE" on the wall above Drebber to confound the investigators. Stangerson, on learning of Drebber's murder, refuses to leave his hotel room. Hope climbs in through the window and gives Stangerson the same choice of pills. However, Stangerson attacks him and Hope stabs him in the heart as an act of self-defence.
Hope dies from his aneurysm on the night after his capture. Holmes reveals to Watson how he deduced the murderer's identity, including a telegram inquiry he had sent to Cleveland in order to gain information about Drebber's background; the reply to it led him to focus on Hope. Outraged at the fact that the newspapers give Lestrade and Gregson full credit for solving the cases, Watson suggests that Holmes publish his own account of the investigation. When Holmes declines, Watson decides to write one himself.