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.
1972
1988
1997
2001
1995
2006
1996
1977
1935
1991
1994
2003
1984
1999
2005
1932
1968
1974
