Edgar said: “Ah.” He was beginning to see how Robert might have been cheated.

Robert took the purse from his belt and opened it. It held a mixture of English and foreign currency. The others waited patiently while he picked out the English coins, all with a cross on one side and the head of King Ethelred on the other. He closed the purse carefully and reattached it to his belt, then counted out the pennies. There were sixty-three.

Aldred said: “Did you win all these coins last night?”

“Most of them,” said Robert.

Wyn said: “Please put sixty pennies in a tray—it doesn’t matter which one.” As Robert did so, Wyn selected some small weights from a box. They were disc-shaped and looked, to Edgar, as if they were made of lead. “Sixty pence should weight exactly three ounces,” Wyn said. He placed three weights in the opposite tray. The tray immediately sank to the bench. Edgar gasped, shocked. Wyn said to Robert: “Your pennies are light.”

“What does that mean?” said Robert.

Edgar knew the answer, but he remained silent while Wyn explained.

“Most silver coins contain some copper to make the disk more hard-wearing,” Wyn said. “English pennies have nineteen parts of silver to one part of copper. Just a moment.” He removed an ounce weight from the tray and began to replace it with smaller ones. “Copper is lighter than silver.” When the two sides balanced he said: “Your pennies contain about ten parts of copper to ten of silver. The difference is so small as to be imperceptible in normal use. But these are forgeries.”

Edgar nodded. That was the solution to the mystery: Wynstan was a forger. And furthermore, Edgar now realized, gambling was a way of changing bad coins for good. If Wynstan won at dice, he gained genuine silver pennies, but if he lost, he only sacrificed forgeries. Over the long run he was sure to come out ahead.

Robert’s face was flushed with anger. “I don’t believe you,” he said.

“I’ll prove it. Does anyone have a good penny?”

Edgar had Dreng’s money. He gave Robert a penny. Robert drew his belt knife and scratched the coin on the side with the head of Ethelred. The scratch was hardly visible.

Wyn said: “That coin is the same all the way through. No matter how deep you go, the color showing will be silver. Now scratch one of your own.”

Robert gave Edgar his penny back, took a coin of his own from the tray, and repeated the exercise. This time the scratch mark was brown.

Wyn explained: “The mixture of half silver, half copper is brown in color. Forgers make their coins look silver by washing them in vitriol, which removes the copper from the surface; but underneath the metal is still brown.”

Robert said furiously: “Those damned Englishmen were gambling with counterfeit money!”

Aldred said: “Well, one of them was.”

“I shall go and accuse Cynred now!”

“Cynred may not be the guilty one. How many were around the table?”