I told her I had left a note for Sir Jeremy and please make sure he got it immediately. As soon as I opened my mouth she turned pale and bobbed a curtsy. “Och, I didna recognize you at first, my lady. How is your dear brother, the duke? Keeping well, I hope.”

“Yes, thank you.” I didn’t really wish to go into the details of the trap. I left her and was walking back to the car but those words continued bouncing around my head. “Your dear brother, the duke.”

And I found myself thinking of a recent time when that same phrase had been used, in a letter to me from Mavis Pugh. Older brother, the Duke of . . . What had she wanted with my brother? What had she wanted to tell me, or ask me? And of course now a nagging doubt crept into my mind. Had she found out something important and was she killed because of it?

Then I remembered that Lady Peebles had also uttered a similar phrasing as we walked up the path toward the grouse moor. She was engaged to the king’s older brother, the Duke of Clarence . . .

The Duke of Clarence, I thought. The eldest son who was so unsuitable, so morally unsound, and who had conveniently died, leaving the throne to the more reliable younger son. And I remembered how Lady Peebles had jumped on Lady Marchmont for mentioning the stupid rumor that he hadn’t actually died, but that he was shut away somewhere. Absurd, of course. Someone in the country would have had to know about this and something would have leaked out by now. It was forty years ago, after all. The Duke of Clarence would now be an old man, almost seventy.

“Right,” I said. “We’ve done all we can do. Let’s go home.” I began the long, winding drive that would take us over the pass and then down to Castle Rannoch. About a mile outside Braemar we passed a tall wrought-iron gate on our left. I had half noticed it before, but not given it a second thought. My mind associated it with some kind of hospital. Now I slowed and noticed there was a plate on the brick wall beside the gate. It said Castle Craig Sanitarium.

I brought the car to a halt and jumped out. “I’ll be right back,” I called.

Beyond the gate a driveway disappeared into trees. I caught just a glimpse of a building beyond. I tried to open the gate, but it was locked.

“You’ll no get in there,” a voice behind me said, and I turned to see an old man with a grinning sheepdog beside him.

“Is it under quarantine because it’s for TB patients?”

He shook his head, a slow smile spreading across his lips. “That’s what they’d like you to think, but it’s for those who are wrong in the head.”