At a party celebrating her eighteenth birthday, Rachel Verinder wears the stunning yellow diamond she unexpectedly inherited from her uncle, Colonel John Herncastle. She is not aware that the precious gem, known as the Moonstone, was plundered from a sacred Hindu shrine in southern India where her uncle had served with the British army fifty years earlier.

But someone knows the secret of the Moonstone and will go to desperate measures to retrieve it. When it goes missing later that night, suspicions are raised and accusations fly. Could it be a trio of mysterious Indian jugglers seen near the house? Or a love-struck housemaid suddely behaving strangely? And there is Rachel herself, who becomes furious when her paramour, Franklin Blake, directs attempts to find it.

As divergent accounts reveal more details, the diamond's recovery is complicated by unexpected twists and turns. Sifting through a compelling list of suspects, the indomitable Sergeant Cuff must find the truth about the Moonstone and its mysterious disappearance.