It is 1849, and Franklin Blake comes back to England after his father's death, forced to face the ghosts of the year before. The famous Indian Moonstone was stolen on the night of Rachel Verinder's 18th birthday and Franklin seeks out the Verinder family butler, for his help in finding the jewel. If he doesn't find it, then Rachel, the love of his life, will be lost to him forever.

Rachel's cousin Miss Clack arrives in Yorkshire and tells Franklin what happened when Rachel and Lady Verinder were reunited in London. She tells how another of Rachel's cousins has been implicated in the disappearance of the Moonstone. He was mysteriously kidnapped and searched by Indian men following a visit to a London bank. Godfrey insists to Rachel that it is a case of mistaken identity. She believes him - should Franklin?

The Verinder's solicitor Mr. Bruff discovers that Godfrey has proposed to Rachel and that the invitation has been accepted. While Bruff heads off to try to stop the wedding, Sergeant Cuff arrives at Franklin's lodgings with a letter from Rosanna. Franklin immediately returns to Yorkshire and makes a perilous trip to the Shivering Sands with Gabriel Betteredge, but the tide is high, the waves are strong and the wind whips up when Franklin enters the sea.

Following a tearful meeting with Rachel, Franklin returns to the Verinder house in Yorkshire to seek answers, meeting Dr Ezra Jennings, who offers to help. Franklin is desperate to find the thief and win back Rachel. Jennings has one solution - Franklin must put his life at risk by restaging of the night of the party in the hope it will prove his innocence once and for all.