Day Before Midnight

Hunter ( The Spanish Gambit ) has written a smoothly believable race-against-time thriller with frightening plausibility. Unidentified military terrorists kidnap welder Jack Hummel from his Maryland home and direct him to cut through a block of titanium to reach a launch key in the South Mountain MX missile site. The president decides to send in the crack Delta assault team, but the man best suited to command them is Col. Dick Puller, who was discredited and disgraced in Iran in 1979. Puller, in turn, must work with the only man who knows the missile silo, its designer, Prof. Peter Thiokol. The leader of ``Aggressor-One'' is discovered to be Russian Military Intelligence chief Arkady Pashin: he is charismatic, reactionary and messianically determined to launch the single MX that will trigger a massive Soviet reply. Part of the fast-moving plot revolves around two abandoned coalmine tunnels, a stupid Russian spy and Thiokol's estranged wife, who unwittingly gave the Russians the plans for South Mountain. The 7 a.m.-to-midnight action flashes cinematically on Delta Force, the crack Russian Spetsnaz troops and various civilians. The book is fun, even if the finale is too drawn-out and a bit preachy: `` . . . the regular people, the Rest of US'' will save us. 40,000 first printing; $40,000 ad budget. (Feb.)