A colder war

A top-ranking Iranian military official is blown up while trying to defect to the West. An investigative journalist is imprisoned for writing an article critical of the Turkish government. An Iranian nuclear scientist is assassinated in Tehran. Each had been recently recruited by Western intelligence. Then MI6's most senior agent in Turkey dies in a puzzling plane crash. Fearing the worst, MI6 brings disgraced agent Tom Kell in from the cold to investigate.