The Defector is Daniel Silva's 9th book in the Gabriel Allon series released on July 21, 2009. The cover depicts the House of Parliament and Big Ben in London indicating the next location for Gabriel's adventures.http://www.danielsilvabooks.com/blog/2008/12/defector-is-coming-july-21-2009.asp This is misinformation as a good portion of the book takes place in Russia, where Gabriel tries to rescue 'The Defector' Grigori Bulganov.
The cover of the paperback printing by Signet (July 2010) depicts St. Basil's Cathedral in Moscow.

The plot involves the kidnapping of Grigori Bulganov, one of the defectors from the previous book, and how Gabriel Allon attempts to save him from the clutches of Ivan Kharkov, the antagonist from the previous book.