For Gabriel Allon it was supposed to be the start of a pleasant weekend in London – a visit to a gallery in St. James's to authenticate a newly discovered painting by Titian. But a pair of deadly bombings in Paris and Copenhagen has already marred this autumn day. And then Gabriel notices a man he believes is about to carry out a third attack, but can only watch as the nightmare unfolds. Haunted by his failure to stop the massacre of innocents, Gabriel returns to his cottage in Cornwall, until a summons brings him to Washington and he is drawn into a confrontation with the new face of global terror.