From the liner notes

Walter Garber (Denzel Washington) is a New York City subway dispatcher whose ordinary day is thrown into chaos by an audacious crime: the hijacking of a subway train. Ryder (John Travolta), the criminal mastermind behind the hijacking and leader of a highly-armed gang of four, threatens to execute the train's passengers unless a large ransom is paid within one hour. As the tension mounts beneath his feet, Garber employs his vast knowledge of the subway system in a battle to outwit Ryder and save the hostages. But there's one riddle Garber can't solve: even if the thieves get the money, how can they possibly escape?