Just as The Second Nun's Tale closes, two strangers, a church canon and his servant (or yeoman), gallop up to the pilgrimage and join it. Before long the Yeoman reveals — half by accident — that the Canon is a thieving alchemist. The Canon flees the company, thereby essentially acknowledging his rascality, and the Yeoman renounces the practice of alchemy. He explains this renunciation to the pilgrims, and to himself as well, in two ways: first, in Part I of his tale, by a discussion of the pride of such alchemists as his master, an intelligent man whose sharp, unreasonable self-delusion leads him into cruelly deceiving other men; and then in Part II, which is a parable that implicitly condemns alchemy on the grounds that it makes men prey to exploitation by all sorts of rascals.
Because neither the Canon nor the Canon's Yeoman is presented in The Prologue, most authorities agree that this prologue and tale were written well after The Prologue.
