A terrorist bomb explodes during a South Korean celebration of the anniversary of the election of its first president. Alarms are raised in Washington. No one is claiming responsibility. The first suspect is North Korea. Could it be making a power play against South Korea and unification? If so, how will the U.S. respond? Paul Hood, Director of the Op-Center, must answer these questions. The Op-Center, a largely autonomous new agency which takes on the government's toughest security problems, is