This article examines the symbolism of the cup in Old English poetry and Old French romance. It argues that the dual symbolism of the cup in the Bible, both the cask of divine wrath and the vessel of mercy, invested the image with a particular dichotomy that was inherited by its metaphoric social functions in the literature of the middle ages. In Old English literature, the cup became a metonym for the contract for lord and thane, the conviviality and treasure exchange that united the mead-hall community. But never far beneath the surface is the fact that this contract requires the thane to die, and this unspoken yet unavoidable truth is writ large in the contagious imagery and vocabulary of the cup. In Old French romance, dichotomy crystallises into binary. The association of the cup of the Last Supper with Joseph of Arimathea, and the development of the Grail legend, made the service of the cup an exclusive loyalty, at the expense of social obligation, and its exigencies are made absolute and immediate. This article offers parallel readings of the same biblical metaphor in different literary cultures and a detailed analysis of a symbol that stands simultaneously for the positive image and its reversal, opposites that are mutually contingent: the community’s desire for unity and preservation and its concomitant fear of disintegration and death.