She was called again to help other monks who had been tortured, but none afflicted her with the same panic as the first one had. She did not save everyone. Sometimes all she could do was ease the agony, stay with them to be there in the last moments. It was never enough.

She hated to be thanked, to accept their gratitude even when she failed. She did not feel brave. She wanted to run away, but the nightmares she would suffer forever, if she left a dying man, would have been worse than any waking horror.

At home she tossed and turned in the night and often woke gasping, her face wet with tears, her lungs aching.

She crept out of bed and knelt in prayer: “Father, help me, teach me. Why do You let this happen? They are good men, peaceable men, trying with all their hearts and bodies, all their time every day, to serve You. Why can’t You help them? Or don’t You care?”

Nothing answered her but the silence, void as the night. If there were real stars, not just dreams and illusion, they were infinitely out of reach.

Once she only just escaped the emperor’s men when they broke into the house, and she ran, half dragged out of the back door by others who were just as passionately against the union. They were willing to forfeit their homes and possessions to rescue the monks who still preached against it and were made martyrs for their faith.

She ran with them through the wind and rain, their feet splashing in the rivulets of water streaming along the gutters, bumping into blind walls and tripping over steps in the darkness. She was pulled along, someone else carrying her bag and her instruments. She had little idea who they were, only gratitude for their courage.

When eventually they burst into a quiet room with an old woman alone beside the fire, she saw in the torchlight that there were three of them, two men and a young woman with long, wet hair.

“You must be more careful,” the woman said, gasping as she struggled to allow the breath into her lungs. “You have answered too many of these calls. They know you now.”

“Why me? Who knows me?” she asked, fighting against the truth.

“Bishop Constantine,” he answered. “People know you are his physician, and you have helped him with the poor.”

No more was said of it. Of course it was Constantine who was behind the rescues, the medicines, the whole resistance of the mass of ordinary people. It had been he who had fought to have Justinian exiled instead of put to death for his involvement in Bessarion’s murder. They were all battling for the same cause, the survival of the faith, the life, the existence of Byzantium, and the freedom to worship as they knew to be right.

She went to Constantine in the quietness of his own house, in the gallery where his favorite icon hung.

“Thank you,” she said simply, standing hungry and bruised, still exhausted in body from the night’s loss and flight, the whole bitter failure of it. “Thank you for all you do, for having the courage to lead us, holding the light high for us to see. I don’t really know how much I care passionately for one faith over another, one creed in the nature of God and the Holy Spirit, but I know absolutely that I care for the love of humanity that Christ taught us. I know with all my heart that it is worth everything we can pay for it. It is worth living and dying for. Without it, in the end the darkness takes everything.”

There was a moment’s prickling silence. She realized what she had said. “If hell were not so deep that it could break your soul, then heaven could not be so high. Would we want God to lower heaven?”

She drew in her breath as he lifted his head from prayer and looked at her.

“Could he ever do that, and still be God?” she asked, although she could have answered it herself.

He said nothing, but he made the sign of the cross in the air.

It did not matter; she did not need his reply.

HELENA HAD A MILD BUT EMBARRASSING AILMENT THAT she preferred Anna to treat rather than the physician she usually called.

It was the middle of the afternoon, and Simonis woke Anna from a briefly snatched rest. She was exhausted from treating the mutilated and dying, and her first instinct when Simonis told her Helena had sent for her was to refuse. How could she ever keep patience with a little irritation to the skin when men were being tortured to death?

“Bessarion’s widow,” Simonis said sharply, looking at Anna’s face. “I know you’re tired.” Her voice softened, but there was still urgency in it and an edge of fear. “You haven’t slept properly for weeks. But you can’t afford to refuse Helena Comnena. She knew Justinian.” She said his name gently. “And his friends.” She did not add any more, but it hung in the air between them.

Helena received Anna in a newly painted, lush room next to her bedchamber. The murals had been redesigned, far closer to the erotic than Bessarion would have allowed. Anna hid her smile.

Helena was dressed in a loose tunic. She had an ugly rash on her arms. At first, she was frightened and polite. Then, as the herbs and advice began to take effect, she was no longer so concerned and her natural arrogance reasserted itself.

“It still hurts,” Helena said sharply, pulling her arm away.

“It will hurt for a little while longer,” Anna told her. “You must keep the ointment on it, and take the herbs at least twice a day.”

“They’re disgusting!” Helena responded, curling her lip. “Haven’t you got anything that doesn’t taste as if you’re trying to poison me?”

“If I were trying to poison you, I would make it sweet,” Anna replied with a slight smile.

Helena paled. Anna saw it and her interest sharpened. Why had Helena mentioned poison so easily? She looked away and allowed the silk of Helena’s robes to fall back into a more modest position.

“Do you really have any idea what you’re doing?” Helena snapped.

Anna decided on the risk. “If you are worried, I know other physicians who might suit you. And I am sure Zoe would know even more.”

Helena’s eyes were bright and hard, her cheeks flushed. She swallowed as if there were something rank in her throat. “I’m sorry. I spoke in haste. Your skill is quite sufficient. I am unused to pain.”

Anna kept her eyes lowered in case Helena saw in them the contempt she felt. “You are right to be apprehensive. Such things, if not treated quickly, can become serious.”

Helena drew in her breath with a little hiss. “Really? How quickly?”

“As you have done.” Anna had exaggerated the danger. “I have another herb here which will help, but if you wish, I will stay with you, so that if it should have any ill effects in other ways, I can give you the antidote.” That was an invention, but it would take time even to broach the subjects she wished to explore.

Helena gulped. “What sort of effects? Will it make me ill?”

“Faint,” Anna replied, thinking of something not too distressing. “Perhaps a little hot. But it will pass quickly, if I give you the herb which counteracts it. You mustn’t take it if it isn’t needed. I’ll stay with you.”

“And charge extra, no doubt!” Helena snapped.

“For the herb, not for the time.”

Helena considered for several seconds, then accepted. Anna mixed a number of herbs for her and had them steeped in hot water. It would be relaxing, good for the digestion. She soothed her conscience by telling herself she had kept her oath: If she was doing no good, at least she was doing no harm.

Helena saw Anna’s eyes on the murals. “Do you like them?” she asked.

Anna drew in her breath. “I’ve seen nothing like them before.”

“Nor in the flesh, I suppose,” Helena observed with a sneer.

Anna longed to say that she had tended patients in a brothel once and seen something of the sort, but she could not afford to. “No,” she said, clenching her teeth.