The Day the Call Came — Thomas Hinde

Though THE DAY THE CALL CAME reads like fantasy, it is far from being that, and just how horrifyingly real it all is becomes clear as the story develops. When the call came, Harry Bale, the nervous eccentric hero, was ready for it. He receives his sinister instructions by letter, telephone, and the winking of car mirrors. But can Harry ever be sure just what his masters mean---or who his enemy is?