Read "The Moonstone" by Wilkie Collins online for free on Textopian. Full text with search, annotations, highlights, and AI-powered reading aids.
As to your cousin's death, then, first.
It appears to be established, beyond any reasonable doubt, that he was killed (while he was asleep, or immediately on his waking) by being smothered with a pillow from his bed -- that the persons guilty of murdering him are the three Indians -- and that the object contemplated (and achieved) by the crime, was to obtain possession of the diamond, called the Moonstone.