“There must be a door somewhere.” Darcy was feeling around carefully. Then he said, “Aha.” Light blinded us as a door swung open. We peered out and found ourselves looking into a small, empty room. The walls were paneled in dark wood, and the only contents of the room were glass-topped cases. It was the butterfly room I had discovered in my tour of Kingsdowne when I met Adrian. Darcy helped me step through, and the door swung shut behind us, now invisible from the rest of the paneling.

“Handy,” Darcy said. “Now we need to find out who might know about this, without giving away that we’ve found it ourselves.”

“Should we tell Fairbotham?” I asked.

“Not yet. Let’s wait and hear what he has found out himself first.”

We came out of the butterfly room without seeing a soul. As we walked down the corridor, we heard voices coming from behind a closed door.

“It wasn’t me. I didn’t do it!” a man’s voice was shouting.

“But you were seen, my lad.” Fairbotham’s voice.

“I told you what happened. I came up the path, planning to have it out with the duke and then I found him lying there, dead. I ran up to the house to report what I’d seen, but suddenly it occurred to me that someone might think that I’d done it.”

Darcy and I moved closer to the door.

“And what exactly did you mean when you said ‘have it out with the duke’?” Fairbotham’s voice inquired.

“Tell him what I thought of him. Tell him that he couldn’t throw out my parents, who had lived in that cottage all their lives. I was prepared to go to the press if necessary—let the world know how he was treating his tenants. The left-wing newspapers would love a story like that.”

“So how do we know that you didn’t have this little confrontation with the duke? That he didn’t laugh at you and tell you to go ahead and do your worst. There was nothing you could do to stop him from doing what he liked with his land. So you were furious. You’d seen the knife before in the tack room. You went and got it and followed him, and at the right moment you stabbed him.”

“I didn’t. I swear!” William’s voice had risen alarmingly now.

“I think you’d better come down to the station with me, my boy.”

“Are you arresting me?” William asked. “You can’t do that. I didn’t do it. You’ve no evidence against me at all.”

“We’ll see about that. Take him to the motorcar, boys, and see what he’d like to tell us after he’s been locked up in a cell for a while.”