She gave him a hard look. Where was this going? She decided she had better defend Mattie anyway. “She has never studied the texts of the ancients, of course. Despite that, her remedies work – sometimes better than those of the monks. I think it’s because she bases her treatments on what has worked previously, rather than on a theory about the humours.”

People standing nearby were listening with curiosity, and some of them now joined in uninvited.

“She gave our Nora a potion that brought her fever down,” said Madge Webber.

John Constable said: “When I broke my arm, her medicine took the pain away while Matthew Barber set the bone.”

Philemon said: “And what kind of spells does she pronounce when she’s making her mixtures?”

“No spells!” Caris said indignantly. “She tells people to pray when they take their medicines, because only God can heal – she says.”

“Could she be a witch?”

“No! It’s a ridiculous idea.”

“Only there has been a complaint to the ecclesiastical court.”

A chill gripped Caris. “From whom?”

“I can’t say. But I’ve been asked to investigate.”

Caris was mystified. Who could Mattie’s enemy be? She said to Philemon: “Well, you of all people know Mattie’s worth – she saved the life of your sister when she gave birth to Sam. Gwenda would have bled to death if not for Mattie.”

“So it seems.”

“Seems? Gwenda’s alive, isn’t she?”

“Yes, of course. So you feel sure Mattie does not call on the devil?”

Caris noticed that he asked the question in a slightly raised voice, as if he wanted to make sure the listeners around heard it. She was puzzled, but she had no doubt of her answer. “Of course I’m sure! I’ll swear an oath if you want.”

“Not necessary,” Philemon said smoothly. “Thank you for your advice.” He inclined his head in a sort of bow, and slithered away.

Caris and Merthin walked towards the exit. “What rubbish!” Caris said. “Mattie a witch!”

Merthin looked troubled. “You would expect Philemon to want evidence against her, wouldn’t you?”

“Yes.”

“So why did he come to you? He could have guessed that you, of all people, would deny the charge. Why would he be keen to clear her name?”

“I don’t know.”

They passed through the great west doorway and out on to the green. The sun was shining on hundreds of stalls loaded with colourful goods. “It doesn’t make sense,” Merthin said. “And that troubles me.”

“Why?”

“It’s like the cause of weakness in the south aisle. If you can’t see it, it may be working away invisibly to undermine you – and you won’t know it until everything comes crashing down all around.”

The scarlet cloth on Caris’s market stall was not as good as that sold by Loro Fiorentino, although you had to have a sharp eye for wool to see the difference. The weave was not so close, because the Italian looms were somehow superior. The colour was just as bright, but it was not perfectly even over the length of the bale, no doubt because Italian dyers were more skilled. In consequence, she charged one-tenth less than Loro.

All the same, it was easily the best English scarlet that had ever been seen at Kingsbridge, and business was brisk. Mark and Madge sold it retail by the yard, measuring and cutting for individual customers, and Caris dealt with wholesale buyers, negotiating reductions for one bale or six with drapers from Winchester, Gloucester and even London. By midday on Monday she knew she would sell out before the end of the week.

When business slowed down for the dinner break she strolled around the fair. She felt a profound sense of satisfaction. She had triumphed over adversity, and so had Merthin. She stopped at Perkin’s stall to talk to the Wigleigh folk. Even Gwenda had triumphed. Here she was, married to Wulfric – something that had seemed impossible – and there was her baby, Sammy, a year old, sitting on the ground, fat and happy. Annet was selling eggs from a tray, as always. And Ralph had gone to France to fight for the king, and might never come back.

Farther on she saw Joby, Gwenda’s father, selling his squirrel furs. There was a wicked man. But he seemed to have lost his power to hurt Gwenda.

Caris stopped at her own father’s stall. She had persuaded him to buy fleece in smaller quantities this year. The international wool market could not possibly thrive when the French and English were raiding one another’s ports and burning ships. “How is business?” she asked him.

“Steady,” he said. “I think I’ve judged it about right.” He forgot that it had been her judgement, not his, that had counselled caution. But that was all right.

Their cook, Tutty, appeared with Edmund’s dinner: mutton stew in a pot, a loaf of bread and a jug of ale. It was important to look prosperous, but not overly so. Edmund had explained to Caris, many years ago, that although customers needed to believe they were buying from a successful business, they would resent contributing to the wealth of someone who appeared to be rolling in money.

“Are you hungry?” he asked her.

“Starving.”

He stood up to reach for the stew pot. Then he staggered, made an odd sound half way between a grunt and a cry, and fell to the ground.

The cook screamed.

Caris cried: “Father!” But she knew he would not respond. She could tell he was unconscious by the way he hit the earth, inertly heavy, like a sack of onions. She fought down the urge to scream. She knelt beside him. He was alive, and breathing hoarsely. She grasped his wrist and felt his pulse: it was strong, but slow. His face seemed flushed. It was always reddish, but now it seemed more so than usual.

Tutty said: “What is it? What is it?”

Caris forced herself to speak calmly. “He’s had a fit,” she said. “Fetch Mark Webber. He can carry Father into the hospital.”

The cook ran off. People from the neighbouring stalls gathered around. Dick Brewer appeared and said: “Poor Edmund – what can I do?”

Dick was too old and fat to lift Edmund. Caris said: “Mark’s coming to take him to the hospital.” She began to cry. “I hope he’ll be all right,” she said.

Mark appeared. He lifted Edmund easily, cradling him gently in his strong arms, and walked towards the hospital, negotiating his way through the crowds, calling: “Mind out, there! Out of the way, please! Injured man, injured man.”

Caris followed, distraught. She could hardly see through her tears, so she stayed close to Mark’s broad back. They reached the hospital building and went inside. Caris was grateful to see the familiar knobbly face of Old Julie. “Fetch Mother Cecilia, as quick as you can!” Caris said to her. The old nun hurried away, and Mark laid Edmund on a pallet near the altar.

Edmund was still unconscious, eyes closed, breathing hoarsely. Caris felt his forehead: he was neither hot nor cold. What had caused this? It had been so sudden. One moment he had been talking normally, the next he fell down unconscious. How could such a thing happen?

Mother Cecilia came. Her bustling efficiency was reassuring. She knelt beside the pallet and felt Edmund’s heart, then his pulse. She listened to his breathing and touched his face. “Get him a pillow and a blanket,” she said to Julie. “Then fetch one of the monk-physicians.”

She stood up and looked at Caris. “He’s had a fit,” she said. “He may recover. All we can do is make him comfortable. The physician may recommend bleeding, but apart from that the only treatment is prayer.”

That was not good enough for Caris. “I’m going for Mattie,” she said.

She ran out of the building and dodged through the fair, remembering that she had done exactly the same thing a year ago, rushing to fetch Mattie when Gwenda was bleeding to death. This time it was her father, and she felt a different kind of panic. She had been desperately worried about Gwenda, but now it was as if the world was falling apart. The fear that her father might die gave her the dreadful feeling she sometimes got in dreams, when she found herself on the roof of Kingsbridge Cathedral with no way down but to jump.