Mary Morstan has received a pearl in the post every year since her father's disappearance. This leads Holmes and Watson to the truth about a secret pact between four convicts during the Indian Rebellion of 1857.
Not streaming on a subscription service in the US right now.
Starring Jeremy Brett, Edward Hardwicke, Jenny Seagrove, Ronald Lacey, John Thaw, Emrys James, Alf Joint, Kiran Shah, Terence Skelton, Rosalie Williams