In the eighteenth century, on discovering her husband has been murdered, an Irish noblewoman drinks handfuls of his blood and composes an extraordinary lament that reaches across centuries to the young Doireann Ní Ghríofa, whose fascination with it is later rekindled when she narrowly avoids fatal tragedy in her own life and becomes obsessed with learning everything she can about the poem Peter Levi has famously called "the greatest poem written...