Rules of Vengeance (Jonathan Ransom #2) by Christopher Reich

The day Jonathan Ransom's wife, Emma, turns up after a brief period of exile ignites a catastrophic series of events which spin his life out of control. Jonathan reluctantly agrees to a reconciliation with Emma after learning of her double life as a spy. But only a day after the reunite, they are caught up in a terrible act of violence: terrorists attack a convoy of limousines carrying the Russian Interior Minister through London. Many are left dead and Emma has gone missing. Both she and Jonathan were caught on CCTV just before the attack, acting in a suspicious manner.

Pursued by MI5, Jonathan knows that the only way to clear his name is to track down his wife and discover why she acted as she did that fateful day. In doing so he hopes to learn once and for all the truth behind her identity. From London to Italy and then to France, Jonathan is at once pursuer, pursued and a pawn in a deadly game of espionage.