The following version of this book was used to create this study guide: Doyle, Sir Arthur Conan. A Study in Scarlet; and The Sign of the Four. Dover Publications, Inc., 2003.

The mystery starts with Part 1. Dr. John Watson and a man named Sherlock Holmes agreed to rent an apartment together. Eventually, Holmes told Watson that he was a consulting detective. Holmes and Watson went together to the house where the corpse of Enoch Drebber had been found. When the corpse was lifted, a woman’s wedding ring fell to the group.

Quickly, Holmes became confident that he knew who had committed the murder. Instead of a professional police force, he had beggar children assist him in his quest to catch the murderer. Two professional detectives, Lestrade and Tobias Gregson, had also tried to solve the mystery, but they could not figure it out. When Gregson, Lestrade, and Watson were together with Holmes at his apartment, a cab driver arrived for Holmes. Holmes asked him to come up to his apartment. Then Holmes arrested him and declared that the man was Jefferson Hope. He was the murderer of Stangerson and Drebber.

Part 2 starts on May 4, 1847. A man named John Ferrier was in the desert. He was parched with thirst. He carried a child named Lucy, who was about five years old. As they were dying in the desert, the Mormons discovered them. The leader of the Mormons was named Brigham Young. He said that they would save John and Lucy only if they joined their religion. Desperately, John agreed.

The Mormons settled in Salt Lake City, Utah. John became wealthy as a diligent farmer. Twelve years later, his adopted daughter, Lucy, matured into a beautiful young woman. She fell in love with a man named Jefferson Hope. He was not a Mormon. Lucy and Jefferson planned to get married within a couple of months.

However, Brigham Young came to John’s home and told him that Lucy must not marry someone who was not a Mormon. He said that Lucy must marry either Joseph Stangerson or Enoch Drebber; both were sons of the elders. Young said that John and Lucy would have only one month to choose which of the two whom Lucy would marry.

Eventually, Jefferson arrived at night to help John and Lucy escape. During their flee, they ran out of food. Lucy and John waited in part of the woods while Jefferson left to hunt for food. However, when Jefferson returned, he discovered that the Mormons had killed John and taken Lucy back with them to Salt Lake City.

When Jefferson returned to Salt Lake City, he learned that Stangerson was the person who had shot and killed John, and that Drebber had married Lucy. Lucy was heartbroken and died quickly within one month. Drebber did not mourn for her. He had married her mainly to obtain her dad’s wealth. Jefferson took the wedding ring from Lucy’s dead finger. He vowed to obtain revenge on behalf of Lucy and John.

Throughout 20 years, Jefferson followed Drebber and Stangerson. He wanted to find each man alone so that he could obtain revenge. He knew that if they were together, they could defend each other. If he could obtain each of them alone, however, he could kill each one and thereby avenge the deaths of Lucy and John. Jefferson followed Drebber and Stangerson throughout the United States and later to Europe.

Next, the narrative continues from Dr. Watson’s journal. It continues from Holmes and Watson’s apartment from the time when Holmes had arrested Jefferson Hope. Jefferson then was kind and friendly toward Holmes, Watson, Gregson, and Lestrade. They went to the police station together. There, Jefferson explained how he had avenged the deaths of John and Lucy Ferrier. Jefferson would soon die from an aneurysm, but he was content and peaceful because he had secured justice for Lucy and John Ferrier by killing Stangerson and Drebber.

The next day, Holmes and Watson read the newspaper. It celebrated Gregson and Lestrade’s work on the case. Holmes was glad that he solved the case, even though he lamented that the newspaper did not recognize his work.