The Wolf at the Door — Jack Higgins

On Long Island, a trusted operative for the president nudges his boat up to a pier, when a man materializes out of the rain and shoots him. In London, General Charles Ferguson, adviser to the prime minister, approaches his car on a side street, when there is a flash and the car explodes. In New York, a former British soldier, who is also a bit more than that, takes a short walk in Central Park to stretch his legs, when a man comes up fast behind him, a pistol in his hand.

And that is only the beginning. Someone is targeting the members of the elite intelligence unit known as "the Prime Minister's private army" and all those who work with them, and whoever is doing it has a lot of resources at his command. Sean Dillon has an idea of who it may be, an old nemesis who has clearly gotten tired of their interference in his schemes. But proving it is going to be a difficult task. And surviving it the hardest task of all. . .