An adaptation of the classic novel by Wilkie Collins, `The Moonstone' is considered the first true detective tale in the English language. On her 18th birthday, Rachel Verinder, a young English woman, inherits a large diamond passed down by her uncle. When the diamond is stolen after a lavish birthday celebration, Rachel's cousin, Franklin Blake, sets out to track down the thief and reclaim the diamond in an effort to win Rachel's affection. Desperate to win the heart of his one true love, Franklin convinces Sergeant Cuff, a celebrated detective, to step out of retirement, and the two embark on a quest to recover the precious gemstone.