Crispin acquires allies and a sidekick, Jack Tucker, an urchin and thief. He saved Jack from the Sheriff and earned his loyalty and service. Jack cleans Crispin's room, mends his clothes, supplies occasional food, and sleeps on straw in a corner of Crispin's room. Jack possesses a variety of useful talents and carries messages for Crispin.

A wealthy mercer hires Crispin to spy on his wife. He fears she is unfaithful. Crispin discovers her with another man, a Saracen. Disappointed, he returns to tell the merchant, but finds him dead in a locked room. The Sheriff demands to know why the mercer hired Crispin, but he refuses to say.

Westerson, like other recent mystery writers, uses the legend of Veronica's Veil, called the Mandyllon, as a key element in several murders. Crispin professes distrust of so-called holy relics. Those in its presence of the Mandyllon must tell the truth.

The mercer's widow hires Crispin to located the Mandyllon she believes is hidden somewhere in the house. At first, he refuses concerned the widow had a motive for murder. However, chronically short of cash and fascinated by the locked room murder and the beautiful widow, he decides to investigate and take the widow's money.

Crispin's background as a knight helps and hinders him. He looks down on the lower class and the widow when he learns she was once a chambermaid. Despite her beauty and spunk, he cannot bring himself to form an alliance with her.

The Sheriff takes umbrage at Crispin, and he also manages to anger his allies and shadowy third parties. He cannot decipher the motives of these and must do so to find the mercer's murderer. Repeated threats, beatings, murder attempts, and imprisonment fail to deter him. Plots within plots confuse his investigations.

Westerson provides plenty of gritty color using the seamy side of London life. Fascinated by noir mysteries and enamored of medieval history, Westerson decided to exploit both with her Crispin Guest novels. The next, the Serpent in the Thorns, will appear next year.