A silver chalice, kept for generations by a family who believed it might be the cup Christ used at the Last Supper, becomes the starting point for a wider search into the Holy Grail legend. The film traces the myth from medieval romance literature, where Arthurian knights first go looking for it, through the churches and reliquaries across Europe that have claimed to hold the real object, including Valencia's cathedral and its own candidate cup. Historians and medievalists walk through what the earliest written sources actually say, how the story mutated as it passed through French poets, Grail-quest legends, and later religious relic trade, and why so many competing chalices exist at all. Interviews and location filming move between archives, cathedrals, and private collections as the film weighs the physical evidence against centuries of accumulated legend. Rather than declaring a winner, it lays out why the Grail's power has always come from the story people needed it to tell, more than from any single object.