On the land side, the walls-twenty-five feet thick-rose in three levels behind a moat sixty feet wide and twenty-two feet deep. Normally dry, the moat was flooded during siege by a series of pipes. The first wall was a low one used to shield a line of archers. The next wall rose twenty-seven feet above the second level and sheltered more troops. Beyond lay the third, and strongest, bulwark. The towers-some seventy feet high-held archers, Greek fire machines, and missile throwers.

On the sea side, Constantinople was protected by a single wall with towers set at regular intervals which also enclosed each of its seven harbors. Across the Golden Horn was stretched a thick chain, which prevented unwelcome ships from sailing up the horn.

And across the horn the two sub-cities of Galata and Pera were also well-walled.

The city was besieged for a year. And for a year its gates remained closed to John Cantacuzene. But the presence of his army on the landward side of the town and the sultan’s fleet sitting off the harbors were beginning to take a toll. Food and other supplies began to dwindle. Cantacuzene’s forces found the source of one of the city’s main aqueducts and diverted it so that Constantinople’s water supply was cut.

Then the plague broke out. The infant daughter who Zoe Cantacuzene had borne in sanctuary died. Frantic that he might lose Theadora and, thus, lose the sultan’s aid, John Cantacuzene arranged an escape from the city for his wife and two youngest daughters.

At the Convent of St. Barbara only two people knew of the departure-the Reverend Mother Thamar and the little nun who kept the gate. The night chosen was during the dark of the moon and, by a fortunate coincidence, there was a storm.

Dressed in the habit of the order that had sheltered them, Zoe and her daughters slipped out into the night and walked to the Fifth Military Gate. Zoe’s heart was hammering wildly and her hand, holding the lantern that lit their way, shook uncontrollably. All her life she had been surrounded by slaves. She had never walked through the city at all, much less gone out unescorted. It was the greatest adventure of her life and, though frightened, she walked with determination, breathing deeply, mastering her fear.