When DC is leveled by a nuclear attack and the President is assassinated, former CIA op Beck Casey rises from the ashes to bring terrorists to justice . . .   "Washington . . . gone."   Ominous words uttered on an Israeli submarine stationed in the Gulf of Oman moments before a torpedo destroys that vessel as well.   A nuclear strike has rendered the American capital a radioactive wasteland. But that's just the beginning of a vast, coordinated terrorist attack. The President falls next. Lone wolf shootings erupt throughout the heartland. Computer viruses take down systems and disable grids across the country.   The stakes have never been higher, as former CIA agent Beck Casey joins forces with an international task force to neutralize a seemingly unstoppable enemy. They've got three days to save the world . . . or die trying.