Defector, paperback/daniel silva

Gabriel Allon is in Umbria, when news reaches him that a Russian defector who saved his life has vanished without trace.

British Intelligence assume he was a double agent, but Allon knows better, and soon finds himself in a deadly duel of wits with a murderous Russian arms dealer.

it grips its reader by the throat like a rampant rottweiler and never, ever lets go }Daily Mail{.