Dark zone - Stephen Coonts

The mission seems routine: go to London, meet someone in a park, obtain a list of computers that are being used secretly by terrorists to pass messages. But just as Deep Black operatives Charlie Dean and Tommy Karr are about to meet their contact, a sniper guns the stranger down.

A Deep Black investigation begins. Former Delta Force trooper Lia DeFrancesca gets called in to help and the three operatives start cracking some leads. But the investigation doesn't kick in to high gear until the murder is found to be connected to a devastating terrorist plot to set off a nuclear warhead in the Chunnel. The explosion will create an earthquake and thus a tsunami that will wipe out the coasts of France and England, killing hundreds of thousands . . .