San Marino, Huntington Library MS HM 64538, an English book of hours (ca. 1425–50), contains a versified Middle English exemplum (laid out as prose) about the efficacy of praying for the dead in Purgatory. This unusual addition to a largely Latin manuscript originated in the thirteenth-century Golden Legend before circulating in Middle English in John Mirk's late-fourteenth-century Festial. A nearly identical version (laid out in verse) appears as part of a series of religious lyrics in London, British Library MS Harley 2251, a poetic anthology closely associated with Lydgate. As an addition to HM 64538, the story reshapes the book as commemorative, and its complex textual biography challenges us to reconsider books of hours as texts that enrich collective worship and as archives of vernacular literary practice and production.