In 1517 the English armies have defeated and killed James IV of Scotland at Flodden and James's widow-queen, Margaret, sister to Henry VIII, has fled to England, leaving her crown under a Council of Regency. Roger Shallot is drawn into a web of mystery and murder by his close friendship with Benjamin Daunbey, the nephew of Cardinal Wolsey, first minister of Henry VIII. Benjamin and Roger are ordered into Margaret's household to resolve certain mysteries as well as to bring about her restoration to Scotland. They begin by questioning Selkirk, a half-mad physician imprisoned in the Tower. He is subsequently found poisoned in a locked chamber guarded by soldiers. The only clue is a poem of riddles. However, the poem contains the seeds for other gruesome murders. The faceless assassin always leaves a white rose, the mark of Les Blancs Sangliers, a secret society plotting the overthrow of the Tudor monarchy.