A deadly bomb goes off in the Wartime Claims and Inquiries office in Vienna. Two people end up in the morgue, one man in Intensive Care. The incident brings art restorer Mario Delvecchio away from his work in Venice to investigate who is behind it. There, he resumes his activities as Gabriel Allon, master Israeli spy (first introduced in THE KILL ARTIST). He wants to find whoever is responsible for the attack as much as his mentor/master, Shamron, and the rest of his Mossad colleagues, especially when he realizes that the man in the hospital is an old and dear friend.