Caris studied the floor, and after a moment said: “I wouldn’t have noticed if you hadn’t told me, but I can see them now. Can they be locked?”

“I suppose they could,” said Godwyn. “But then it would be obvious where they were, which would defeat the purpose of hiding them under flagstones.”

“But this way the monks and nuns have access to one another’s money.”

Philemon spoke up. He looked accusingly at Caris and said: “Why are you here? You’re the guest master – nothing to do with the treasury.”

Caris’s attitude to Philemon was simple loathing. She felt he was not fully human. He seemed to have no sense of right and wrong, no principles or scruples. Whereas she despised Godwyn as a wicked man who knew when he was doing evil, she felt that Philemon was more like a vicious animal, a mad dog or a wild boar. “I have an eye for detail,” she told him.

“You’re very mistrustful,” he said resentfully.

Caris gave a humourless laugh. “Coming from you, Philemon, that’s ironic.”

He pretended to be hurt. “I don’t know what you can mean.”

Beth spoke again, trying to keep the peace. “I just wanted Caris to come and look because she asks questions I don’t think of.”

Caris said: “For example, how can we be sure that the monks don’t take the nuns’ money?”

“I’ll show you,” said Beth. Hanging on a hook on the wall was a stout length of oak. Using it as a lever, she prised up a flagstone. Underneath was a hollow space containing an ironbound chest. “We’ve had a locked casket made to fit each of these vaults,” she said. She reached inside and lifted out the chest.

Caris examined it. It seemed strongly made. The lid was hinged, and the clasp was secured by a barrel padlock made of iron. “Where did we get the lock?” she asked.

“Christopher Blacksmith made it.”

That was good. Christopher was a well-established Kingsbridge citizen who would not risk his reputation by selling duplicate keys to thieves.

Caris was not able to fault the arrangements. Perhaps she had worried unnecessarily. She turned to go.

Elfric appeared, accompanied by an apprentice with a sack. “Is it all right to put up the warning?” Elfric said.

Philemon replied: “Yes, please, go ahead.”

Elfric’s assistant took from his sack something that looked like a big piece of leather.

Beth said: “What’s that?”

“Wait,” said Philemon. “You’ll see.”

The apprentice held the object up against the door.

“I’ve been waiting for it to dry out,” Philemon said. “It’s Gilbert Hereford’s skin.”

Beth gave a cry of horror.

Caris said: “That’s disgusting.”

The skin was turning yellow and the hair was falling out of the scalp, but you could still make out the face: the ears, two holes for the eyes, and a gash of a mouth that seemed to grin.

“That should scare thieves away,” Philemon said with satisfaction.

Elfric took out a hammer and began to nail the hide to the treasury door.

The two nuns left. Godwyn and Philemon waited for Elfric to finish his gruesome task, then they went back inside the treasury.

Godwyn said: “I think we’re safe.”

Philemon nodded: “Caris is a suspicious woman, but all her questions were answered satisfactorily.”

“In which case…”

Philemon closed the door and locked it. Then he lifted the stone slab over one of the nuns’ two vaults and took out the chest.

“Sister Beth keeps a small amount of cash for everyday needs somewhere in the nuns’ quarters,” he explained to Godwyn. “She comes in here only to deposit or withdraw larger sums. She always goes to the other vault, which contains mostly silver pennies. She almost never opens this chest, which contains the bequest.”

He turned the box around and looked at the hinge at the back. It was fixed to the wood by four nails. He took from his pocket a thin steel chisel and a pair of pliers for gripping. Godwyn wondered where he had got the tools, but did not ask. Sometimes it was best not to know too many details.

Philemon slipped the sharp blade of the chisel under the edge of the iron hinge and pushed. The hinge came away from the wood slightly, and he pushed the blade in a little farther. He worked delicately and patiently, careful to make sure that the damage would not be visible to a casual glance. Gradually the flat plate of the hinge became detached, the nails coming out with it. When he had made enough room for the pliers to grip the nailheads, he pulled them out. Then he was able to detach the hinge and lift the lid.

“Here’s the money from the pious woman of Thornbury,” he said.

Godwyn looked into the chest. The money was in Venetian ducats. These gold coins showed the Doge of Venice kneeling before St Mark on one side and, on the other, the Virgin Mary, surrounded by stars to indicate that she was in heaven. Ducats were intended to be interchangeable with florins from Florence, and were the same size, weight and purity of metal. They were worth three shillings, or thirty-six English silver pennies. England had its own gold coins now, an innovation of King Edward’s – nobles, half-nobles and quarter-nobles – but these had been in circulation less than two years, and had not yet displaced foreign gold coins.

Godwyn took fifty ducats, worth seven pounds and ten shillings. Philemon closed the lid of the chest. He wrapped each of the nails in a thin strip of leather, to make them a tight fit, and reattached the hinge. He put the chest back in the vault and lowered the slab over the hole.

“Of course they will notice the loss, sooner or later,” he said.

“It may not be for years,” Godwyn said. “We’ll cross that bridge when we come to it.”

They went out, and Godwyn locked the door.

Godwyn said: “Find Elfric, and meet me in the cemetery.”

Philemon left. Godwyn went to the eastern end of the graveyard, just beyond the existing prior’s house. It was a blowy May day, and the fresh wind made his robe flap around his legs. A loose goat was grazing among the tombstones. Godwyn watched it meditatively.

He was risking a terrible row with the nuns, he knew. He did not think they would discover their loss for a year or more, but he could not be sure. When they did find out, there would be hell to pay. But what, exactly, could they do? He was not like Gilbert Hereford, stealing money for himself. He had taken the bequest of a pious woman to use for holy purposes.

He thrust his worries aside. His mother was right: he needed to glorify his role as prior of Kingsbridge if he was going to make further progress.

When Philemon returned with Elfric, Godwyn said: “I want to build the prior’s palace here, well to the east of the present building.”

Elfric nodded. “A very good location, if I may say so, lord prior – close to the chapter house and the east end of the cathedral, but separated from the market place by the graveyard, so you’ll have privacy and quiet.”

“I want a big dining hall downstairs for banquets,” Godwyn went on. “About a hundred feet long. It must be a really prestigious, impressive room, for entertaining the nobility, perhaps even royalty.”

“Very good.”

“And a chapel at the east end of the ground floor.”

“But you’ll be just a few steps from the cathedral.”

“Noble guests don’t always want to expose themselves to the people. They must be able to worship in private if they wish.”

“And upstairs?”

“The prior’s own chamber, of course, with room for an altar and a writing desk. And three large chambers for guests.”

“Splendid.”

“How much will it cost?”

“More than a hundred pounds – perhaps two hundred. I’ll make a drawing then give you a more accurate estimate.”

“Don’t let it go above a hundred and fifty pounds. That’s all I can afford.”

If Elfric wondered where Godwyn had suddenly acquired a hundred and fifty pounds, he did not ask. “I’d better start stockpiling the stone as soon as possible,” he said. “Can you give me some money to begin with?”