Multi-lingual Israeli spy/art restorer Gabriel Allon is restoring a painting in Venice when a bomb destroys the 'Wartime Claims and Inquiries Office' in Vienna, Austria. Gabriel's friend Eli Lavon is badly wounded and Eli's staff is killed. When Gabriel travels to Vienna to investigate he meets an elderly Holocaust survivor who claims that a prominent, wealthy, local businessman - Ludwig Vogel - is really a Nazi war criminal named Erich Radek.
Before long the elderly Holocaust survivor is murdered and Gabriel's further inquiries - which require trips to the Vatican and Argentina - seem to confirm that Vogel is indeed Radek. Gabriel suspects that the bombing and murder were perpetrated to prevent Vogel/Radek from being exposed - and there's a little side-story associated with this presumption. Along the way Gabriel learns more about his mother, a Holocaust survivor who's been very reluctant to speak about her wartime experiences. This makes Gabriel even more determined to bring Radek to justice.
During Gabriel's travels there are several attempts on his life but none are successful due to a little help from his friends. These various friends also help Daniel hatch up a complex scheme to snatch Radek, and this leads to the book's dramatic climax.
As usual in Daniel Silva's writing, the book has a political bent. In this story, the Vatican, the Catholic Church, and Pope Pius XII are depicted as having collaborated with the Nazis and having helped war criminals escape. Also, Austria is described as having been sympathetic to the Nazis, with people willing to run concentration camps and cover up war crimes. FYI: The parts of the book that described Nazi treatment of the Jews are graphic and disturbing.
There are an array of interesting characters in this thriller, including Gabriel's art mentor, his girlfriend, a clock restorer/assassin, residents of the Vatican, members of Israeli's intelligence service, and more. The story is fast-paced with plenty of action, but there aren't a lot of twists. Spy thrillers aren't my favorite genre but I enjoyed the book. Recommended for thriller fans.