Part of the premise for Passager is taken from history. Yolen explains: In the Middle Ages, because of wars of famine or plague, many children were actually abandoned in the woods. There they were left to—in the Latin ecclesiastical phrase—aliena misericordia—the kindness of strangers. Historically, until the eighteenth century, the rate of known abandonments in some parts of Europe was as high as one in four children, an astonishing and appalling figure.

Although the opening passages of Passager only hint at why Merlin is abandoned, Yolen seems to play on the varying stories of his birth. One common myth is that he was the product of a rape, which would make him an outcast at birth in medieval Christian Europe. Sometimes the rapist is a demon or Satan himself and the victim a chaste woman, in at least one version...