A girl named Mary Morstan comes to Sherlock Holmes and asks him and the doctor to help her solve the mystery of how she receives one pearl every year in a parcel and to find her father, who disappeared many years ago. Holmes and Watson do not refuse to help her and find out that Miss Mary is the heiress to a huge fortune - the treasures of Agra, which are also claimed by the sons of Major Sholto and Jonathan Small - an escaped convict with a wooden prosthesis instead of a leg, whom the elder Morstan and Sholto deceived...
