"This is news to me," he said. "Can you tell me more?"

When the Duke said this, I was very surprised, but Holmes was surprised too.

The Duke stood up, and walked round the room for a minute. "I must tell you everything," he said. "I didn't want to talk about it, but I must. I see that now."

He sat down again, and began his story. "When I was a young man, Mr Holmes, I was in love -- oh, so much in love. It only happens to you once, and this woman was the love of my life. I wanted her to be my wife -- but she died. She left me this one child, and I loved him because of her. When I look in his face, I see her, and remember her, and can't stop loving her. I must have the boy near me because of this. But a government minister cannot tell the world about a love-child like this. So, to the world, James is my young secretary, not my son.

"He knows that I am his father. He hates the Duchess, because she is not his mother. And he hates my younger son, Arthur, because Arthur has everything. Arthur has a name, a famous father, houses, money, everything. James has nothing. Well, he has some money, of course, but he is just Mr James Wilder, and he wants to be the Duke of Holdernesse one day. That's not possible, of course, but James can't understand that. And so, you see, I was afraid for Arthur, and that's why I sent him to Dr Huxtable's school.

"And what does James do next? He kidnaps my poor Arthur. It changes nothing, but James can't see that. He wants me to say, "Yes, James, now you can be my first son; you can have everything. Arthur can be the number two son." But I can't do that, of course I can't.

"James knew this man Hayes, you see, because Hayes worked for me once. James asked for Hayes's help, and the man was happy to do it. You remember my letter to Arthur on that last day? Well, James opened the letter and put in a note from him. That evening he cycled across the moor and met Arthur in Ragged Shaw. He talked about the Duchess, Arthur's mother. "She wants to see you," he told Arthur. "She's waiting on the moor. Come back at midnight, and a man with a horse can take you to her." Of course, poor Arthur wanted to see his mother, so he came. Hayes was there with two horses, and they rode across the moor. But the German teacher followed them, and Hayes killed him. Hayes then took Arthur to the Green Man.

"Well, Mr Holmes, I knew nothing about any of this until the murder. James is a bad boy, but he does not murder people. When he heard the news, he came to me at once, crying. What could I do? I didn't want the world to know about this. So James went down to the Green Man. He told Hayes to run away, because everybody knew about the murder now -- and knew the murderer's name too. Hayes left at once. Later, I went down and saw Arthur. I left him there with Mrs Hayes because I couldn't say anything to the police just then.

Holmes quickly wrote a note and took it out of the room. A minute later, he was back. "Now, what are you going to do about Mr James Wilder?" he said.

Holmes stood up. "Well," he said, "Watson and I can go home now, I think. There is just one other small thing… This man Hayes took two horses across the moor, but the horses' feet made the tracks of a cow in the mud. How was this possible?"

"First," said Holmes, "we must bring Arthur home."

"Yes," the Duke said quietly.

"Yes. I wrote to the Duchess this morning."

"Good," said Holmes. "And the Duchess? Perhaps without James in the house, you and she…"

The Duke looked surprised and thought for a minute. Then he went away and came back two minutes later with a glass box in his hands. In the box were some horse-shoes.

"So, Mr Holmes, now you know everything."

"I understand you, Mr Holmes," said the Duke. "James is leaving me and going to Australia next week."

"Mmm," said Holmes. "You help a murderer, you say nothing to the police, you leave your young son in a dirty inn… and you ask for my help."

People never spoke to the Duke of Holdernesse like this usually. His face was red, but he said nothing.

Holmes opened the box and took out one shoe. It was a shoe for a horse's foot, but it looked like a cloven cow's foot. Holmes wet his finger and ran it round the bottom of the shoe. A little mud came off on his finger.

"Thank you," said Holmes. He put the horse-shoe back in its box. "That shoe is the second most interesting thing in the north of England," he said.

"And the first?" asked the Duke.

Holmes took the cheque for twelve thousand pounds from the table, and slowly put it into his notebook, "I am a poor man," he said. He looked lovingly at the notebook, then put it carefully in his pocket.

"We found these shoes under the ground in the garden," the Duke said. "They are about five hundred years old, we think. The Holdernesse family has a long and interesting past."