Pieces, pieces, Katāros thought, as he climbed the stone steps that led up to the Scriptorium. It was the player with the most pieces on the board who controlled the game. And he fancied that in the slender form of this northern queen, he had won himself a piece of considerable worth.

It remained to be seen how she could be used to his advantage. But he was in no doubt that she was now his to manoeuvre. It hadn’t needed more than a little cursory kindness. A set of rooms, a change of attire, a meal, a servant – carefully selected by him, of course – and the promise of an audience with the emperor. After that, gratitude came pouring out of her like a mountain stream in spring.

That she would get what she had come to the Great City for, he doubted. But beauty had its own currency – he of all people knew that – and he intended to expend her wisely. Meanwhile, he had other pieces to gather.

He entered the Scriptorium.

The silence here was unlike the silence of the basilicas – with their heavy solemnity, their air laced with incense, their great looming spaces filled with the presence of that one unendurable question. No. The silence of the Scriptorium was honest. He felt no fear here, only the ghost-thoughts of the minds who had gone before, who had taken a bench and opened a scroll.

His gaze rose to the vaulted ceilings, along the soaring arches and down the shining black pillars to the banks of shelving. Somewhere among them was another piece of the game. Another answer. And it wore on him like a thirst. He inhaled the scent of the tallow lamps and musky parchment, readying himself. If he had to scour every record in the place, he would find the answer.

For three nights, the librarians brought him pile after pile of documents and codices. Architectural plans, audits for the city garrison, military logs, histories, annals, tax records, legal codes, edicts of the Church, administrative protocols, imperial doxologies. Anything that made reference to the land walls. A forest of words through which he prowled like a wolf hunting down his prey. He read till his eyes blurred, till his neck and shoulders were stiff as bark, and on the fourth night, in the dead hours before the dawn, he found it.

A simple note from the palace sakellarios to the deacon of the Church of St Mary of Blachernae, accompanying an endowment from the Emperor Justinian, second of his name, to that church.

To the Holy Virgin and Mother of God – who opened the gates to blessing and glory when all were sealed – His Imperial Majesty bequeaths this gift of five thousand solidi in furtherance of the Glory of Her Name and that of the Most High God and His Most Righteous Son Christ Jesus. . . etc., etc.