The arrival of the annual St Peter’s Fair in Shrewsbury brings a surge of commerce and chaos, which is abruptly shattered by the discovery of a murdered merchant. Brother Cadfael, a monk with a worldly past and a keen eye for human nature, must navigate the crowded fairgrounds to identify the killer of Master Thomas. He faces opposition from local authorities and the complex social hierarchies of the medieval merchant class. The narrative unfolds through a third-person perspective that emphasizes the sensory details of the 12th-century setting and the methodical nature of Cadfael’s investigation.

This novel is widely regarded as a quintessential entry in the Brother Cadfael series, praised for its meticulous historical research and the steady, observant nature of its protagonist. Readers often note the author's ability to ground complex mysteries in the tangible realities of medieval life, making the setting feel as vital as the characters themselves. The narrative style is frequently described as measured and thoughtful, eschewing sensationalism in favor of logical deduction and human insight. It remains a standard-bearer for historical mystery, appreciated for its consistency in tone and the depth of its period-accurate world-building.