They climbed the unrailed stone steps slowly, clinging in the strong wind, to the side of the tower. Once Helena slipped, and she whimpered in fright. Theadora grasped her older sister and shoved her to her feet. Finally they reached their goal. Pushing the door open, they entered the guardroom.

The captain took the parchment from Zoe’s slim white hand.

“Are you a doctor?” he asked. In Byzantium it was not unusual for women to be doctors.

“Yes, captain.”

“Would you look at one of my men? I think he may have broken a bone in his wrist today in a fall.”

“Of course, captain,” said Zoe kindly, and with more assurance than she felt. “But might I do so on my return? Your man’s case is not desperate, and the woman we go to attend is the young wife of a childless old merchant. The gentleman has always been very generous to St. Barbara’s, and his anxiety is great.”

Theadora listened in utter amazement. Zoe’s voice was calm, and her story plausible. At that moment Theadora’s respect for her mother increased a hundredfold.

“He is in pain, sister,” said the captain.

Zoe drew a small box from her robes and shook out two small gilded pills. “Have your man take these,” she said. “It will ease his pain, and he will sleep until I return.”

“My thanks, good sister. Trooper Basil! Escort the doctor and her nuns out the moat postern.” Saluting neatly, the captain bade them a safe journey.

Silently they followed the soldier down several flights of stairs into a long stone corridor, the walls of which were wet and green with slime. It was damp and bone-chilling cold in the tunnel. The corridor was lit at intervals by smoking pitch torches stuck into rusting iron wall holders.

“Where are we?” asked Zoe of their guide.

“Beneath the walls, sister,” came the reply. “I’ll let you out a small postern gate on the other side of the moat.”