Four days before the dedication of the new Freedom Tower at ground zero in New York City, five passengers and a flight attendant bravely foil the hijacking of a commercial jet en route to the city. Thrust into the national spotlight, 'The Six' become instant celebrities, hailed for their bravery. But iconoclastic New York Police investigator Jeremy Fisk believes there's more to this than a simple open-and-shut terrorism case. Fisk -from the department's Intelligence Division - suspects that in reality this is an early warning signal that another potentially more devastating attack is imminent. Fisk and his team spring into action, but as each promising new lead fizzles to nothing they realise that their opponents are smarter and more dangerous than anyone they've faced before. The seemingly invisible enemy is able to exploit every security weakness, anticipating Fisk's every move. And time is running out until ground zero day.