By eleven o'clock, the high mountain wind was screaming through the battlements, carrying fine needles of ice that rattled against the thick glass panes of the upper watchtower.

Nila stood by the narrow slit window, her fingers wrapped around the rough stone ledge. She had refused to return to her quarters after her dinner of dried venison. Instead, she had climbed the spiral staircase to the highest point of the northern palisades, a solitary gray figure silhouetted against the dark masonry.

Below her, the inner courtyard was alive with a silent. There were no torches lit; the risk of alerting Richard’s ridge scouts was too high. The vanguard warriors moved...