Franklin decides that he should go back to London and discuss the situation with Mr. Bruff, the family lawyer.
He has also resolved to meet with Rachel, tricking her if she won't agree to a regular meeting, to ask her to explain why she's so angry with him.
Franklin walks to the train station, accompanied by Betteredge.
As they arrive at the train station, Franklin asks Betteredge whether he were drunk on the night of Rachel's birthday – maybe that would explain how he could have stolen the diamond without having been aware of it.
Betteredge says no – Franklin never drinks more than a glass or two of wine, even on special occasions like Rachel's birthday party.
The only thing that was unusual was that Franklin had had some brandy and water before bed, since he hadn't been sleeping well lately – but it wasn't much, and there's no way it could have made him drunk.
Then Franklin asks Betteredge whether, to his knowledge, he's ever walked in his sleep (after all, Betteredge knew him when he was a kid).
Betteredge points out that even if Franklin had been drunk, or sleepwalking, when he took the diamond, that doesn't account for what happened since then. How did the diamond get to London to be pledged with Mr. Luker?
Franklin then approaches Mr. Bruff to ask him about Rachel's behavior.
He shows Mr. Bruff the nightgown.
Mr. Bruff admits that Rachel thinks that Franklin stole the Moonstone.
But he points out that there's no evidence that Franklin was the one wearing the nightgown the night that it got the paint smeared on it.
And he wonders whether Rosanna might have shown the nightgown to Rachel in order to improve her own chances with Franklin.
Franklin remembers that Rachel might still have been angry with him about some debts that he had made in Paris – she thought he was irresponsible with money, which might have made her more likely to believe that he'd steal the diamond.
Franklin wants to question Rachel himself, and asks Mr. Bruff to invite Rachel to his house, without telling her that she'd see Franklin there.
Mr. Bruff agrees, but reluctantly. He doesn't like the idea of tricking Rachel.
The next day, Mr. Bruff tells Franklin the plan: Rachel will be by herself in the drawing room, and all Franklin has to do is let himself into the house through the back door and ambush her.