‘Why didn’t you tell me this before?’ Luca demanded. ‘When I opened the inquiry? Why keep this back?’

‘Because this place is my life,’ she said fiercely. ‘It has been a beacon on the hill, a refuge for women and a place to serve God. I hoped that the Lady Abbess would learn to live here in peace. I thought God would call her, that her vocation would grow. Then I hoped that she would be satisfied with making a fortune here. I thought she might be an evil woman, but that we might contain her. But since a nun has died – in our care—’ She choked on a sob. ‘Sister Augusta, one of the most innocent and simple women who has been here for years—’ She broke off.

‘Well, now it is all over,’ she said with dignity. ‘I can’t hide what she is doing. She is using this place of God to hide her fortune-hunting, and I believe that her slave is practising witchcraft on the nuns. They dream, they sleepwalk, they show strange signs, and now one has died in her sleep. Before God, I believe that the Lady Abbess and her slave are driving us all mad so that they can get at the gold.’

Her hand sought the cross at her waist and Luca saw her hold it tightly, as if it were a talisman.

‘I understand,’ he said, as calmly as he could, though his own throat was dry with superstitious fear. ‘I have been sent here to end these heresies, these sins. I am authorised by the Pope himself to inquire and judge. There is nothing that I will not see with my own eyes. There is nothing I will not question. Later this morning I will speak to the Lady Abbess again and, if she cannot explain herself, I will see that she is dismissed from her post.’

‘Sent away from here?’

He nodded.

‘And the gold? You will let the abbey keep the gold so that we can feed the poor and establish a library? Be a beacon on the hill for the benighted?’

‘Yes,’ he said. ‘The abbey should have its fortune.’

He saw her face light up with joy. ‘Nothing matters more than the abbey,’ she assured him. ‘You will let my sisters stay here and live their former lives, their holy lives? You will put them under the discipline of a good woman, a new Lady Abbess who can command them and guide them?’

‘I will put it under the charge of the Dominican brothers,’ Luca decided. ‘And they will harvest the gold from the stream and endow the abbey. This is no longer a house in the service of God, as it has been suborned. I will put it under the control of men, there will be no Lady Abbess. The gold shall be restored to God, the abbey to the brothers.’

She gave a shuddering sigh and hid her face in her hands. Luca stretched his hand towards her to comfort her and only a warning glance from Freize reminded him that she was still in holy orders and he should not touch her.

‘What will you do?’ Luca asked quietly.

‘I don’t know. My whole life has been here. I will serve as Lady Almoner until we come under the command of the Brothers. They will need me for the first months, no-one but me knows how this place is run. Then perhaps I will ask if I may go to another order. I would like an order that was more enclosed, more at peace. These have been terrible days. I want to go to an order where the vows are kept more strictly.’

‘Poverty?’ Freize asked at random. ‘You want to be poor?’

She nodded. ‘An order that respects the commands, an order with more simplicity. Knowing that we were storing a fortune of gold in our own loft . . . not knowing what the Lady Abbess was doing or what she intended, fearing she was serving the Devil himself . . . it has been heavy on my conscience.’

The bell tolled the call to chapel, echoing in the morning air. ‘Prime,’ she said. ‘I have to go to church. The sisters need to see me there.’

‘We’ll come too,’ Luca said.

They closed the door to the storeroom and locked it behind them. While Luca watched, she turned to Freize and held out her hand for his key. Luca smiled at her simple dignity as she stood still while Freize patted his pockets in a pantomime of searching, and then, reluctantly, handed over the key. ‘Thank you,’ she said. ‘If you want anything from the abbey stores you may come to me.’

Freize gave a funny little mock bow, as if to recognise her authority. She turned to Luca. ‘I could be the new Lady Abbess,’ she said quietly. ‘You could recommend me for the post. The abbey would be safe in my keeping.’

Before he could answer she looked beyond him at the windows of the hospital, suddenly paused, and put her hand on Luca’s sleeve. At once he froze, acutely aware of her touch. Freize behind him stopped still. She held her finger to her lips for silence and then slowly pointed ahead. She was indicating the mortuary beside the hospital, where a little light gleamed from the slatted shutters, and they could see someone moving.

‘What is it?’ Luca whispered. ‘Who is in there?’

‘The lights should be shielded, and the nuns should be still and silent in their vigil,’ she breathed. ‘But someone is moving in there.’

‘The sisters, washing her?’ Luca asked.

‘They should have finished their work.’

Quietly, the three of them moved across the yard and looked in the open door to the hospital. The door leading from the hospital ward through to the mortuary was firmly closed. The Lady Almoner stepped back, as if she were too afraid to go further.

‘Is there another way in?’

‘They take the pauper coffins out through a back door, to the stables,’ she whispered. ‘That door may be unbolted.’

Quickly, they crossed the stable yard to the double door to the mortuary, big enough for a cart and a horse, barred by a thick beam of wood. The two young men silently lifted the beam from its sockets and the door stood closed, held shut only by its own weight. Freize lifted a useful pitchfork from the nearby wall, and Luca bent and took his dagger from the scabbard in his boot.

‘When I give the word, open it quickly,’ he said to the Lady Almoner. She nodded, her face as white as her veil.

‘Now!’

The Lady Almoner flung the door open, the two young men rushed into the room, weapons at the ready – then fell back in horror.

Before them was a nightmare scene, like a butcher’s shop, with the butcher and his lad working over a fresh carcass. But it was worse by far than that. It was not a butcher, and it was no animal on the slab. The Lady Abbess was in a brown working gown, her head tied in a scarf, and Ishraq was in her usual black robe covered with a white apron. The two girls had their sleeves rolled up, and were bloodstained to the elbows, standing over the dead body of Sister Augusta, Ishraq wielding a bloodied knife in her hand, disembowelling the dead girl. The nuns keeping vigil were nowhere to be seen. As the men burst in, the two young women looked up and froze, the knife poised above the open belly of the dead nun, blood on their aprons, blood on the bed, blood on their hands.

‘Step back,’ Luca ordered, his voice ice-cold with shock. He pointed his dagger at Ishraq, who looked to the Lady Abbess for her command. Freize raised his pitchfork as if he would spear her on the tines.

‘Step back from that body, and no-one will be hurt,’ Luca said. ‘Leave this – whatever it is that you are doing.’ He could not bear to look, he could not find the words to name it. ‘Leave it, and step against the wall.’

He heard the Lady Almoner come in behind him and her gasp of horror at the butchery before them. ‘Merciful God!’ She staggered and he heard her lean against the wall, then retch.

‘Get a rope,’ Freize said, without turning his head to her. ‘Get two ropes. And fetch Brother Peter.’

She choked back her nausea. ‘What in the name of God are you doing? Lady Abbess, answer me! What are you doing to her?’

‘Go,’ said Luca. ‘Go at once.’

They heard her running feet cross the cobbles of the stable yard as the Lady Abbess raised her eyes to Luca. ‘I can explain this,’ she said.

He nodded, gripping the dagger. Clearly, nothing could explain this scene: her sleeves rolled to her elbows, her hands stained red with the blood of a dead nun.

‘I believe that this woman has been poisoned,’ she said. ‘My friend is a physician—’

‘Can’t be,’ Freize said quietly.

‘She is,’ the Lady Abbess insisted. ‘We . . . we decided to cut open her belly and see what she had been fed.’

‘They were eating her.’ The Lady Almoner’s voice trembled from the doorway. She came back into the room, Brother Peter white-faced behind her. ‘The two of them were eating her in a Satanic Mass. They were eating the body of Sister Augusta. Look at the blood on their hands. They were drinking her blood. The Lady Abbess has gone over to Satan and she and her heretic slave are holding a Devil’s Mass on this, our sanctified ground.’

Luca shuddered and crossed himself. Brother Peter stepped towards the slave with a rope held out before him. ‘Put down the knife and put out your hands,’ he said. ‘Give yourself up. In the name of God, I command you, demon or woman or fallen angel, to surrender.’

Holding Freize’s gaze, Ishraq put down the knife on the bed beside the dead nun, then suddenly darted for the doorway that led into the empty hospital. She flung it open and was through it, followed in a moment by the Lady Abbess. As Luca and Freize raced after the two young women, she led the way, running across the yard to the main gate.

Luca bellowed to the porteress, ‘Bar the gate! Stop thief!’ and flung himself on the Lady Abbess as she sprinted ahead of him, bringing her down to the ground in a heavy tackle and knocking the air out of her. As they went down, her veil fell from her head and a tumble of blonde hair swept over his face with the haunting scent of rosewater.

The Moorish slave was half way up the outer gate now, springing from hinge to beam like a lithe animal, as Freize grabbed at her bare feet and missed, and then leaped up and snatched a handful of her robe and tore her off the gate, bringing her tumbling down to fall backwards on the stone cobbles with a cry of pain.