The Moonstone (1868) by Wilkie Collins is a 19th-century British epistolary novel. It is an early example of the modern detective novel, and established many of the ground rules of the modern genre.

Rachel Verinder, a young English woman, inherits a large Indian diamond on her eighteenth birthday. It is a legacy from her uncle, a corrupt British army officer who served in India. The diamond is of great religious significance and extremely valuable. Rachel's eighteenth birthday is celebrated with a large party at which the guests. She wears the Moonstone on her dress that evening for all to see, including some Indian jugglers who have called at the house. Later that night the diamond is stolen from Rachel's bedroom, and a period of turmoil, unhappiness, misunderstandings and ill luck ensues. Told by a series of narratives from some of the main characters, the complex plot traces the subsequent efforts to explain the theft, identify the thief, trace the stone and recover it.