When last we encountered Gabriel Allon, the master art restorer and sometime officer of Israeli intelligence, he had just prevailed in his blood-soaked duel with Saudi terrorist financier Zizi al-Bakari. Now Gabriel is summoned once more by his masters to undertake what appears to be a routine assignment: travel to Amsterdam to purge the archives of a murdered Dutch terrorism analyst who also happened to be an asset of Israeli intelligence. But once in Amsterdam, Gabriel soon discovers a conspiracy of terror festering in the city's Islamic underground, a plot that is about to explode on the other side of the English Channel, in the middle of London.