We're expected to be perfect every single day. We're dealing with millions of people and it only takes one person to delay everything. It could be a sick passenger. It could be a crime.

Just because his train disappears underground, doesn't mean trouble won't follow. On a normal day, Abe's biggest concern isn't terrorists, it's his fellow citizens.

The New York is New York. We have crime up here and down there, just like we do in the streets. Anything that happens in the street happens in the subway. The subway also carries its own built-in hazards. In 1991, five people were killed and more than 200 injured when a train derailed in Manhattan. In 2000, 66 people were injured when another train derailed in Brooklyn. Accidents on the subway are like farms in Manhattan, a rarity. Get no motorman can take the throttle without looking over his shoulder as the disasters that struck other systems. 1975, a crowded rush-hour train crashes into a dead end on the London underground-- 43 people die. 1995, the worst subway disaster in history, in the capital of Azerbaijan, a crowded subway train catches fire in a tunnel--some 300 hundred people perish. Then there is terrorism. French police blame radical Muslims for a 1995 attack on the Paris metro. Russian police suspect terrorists in the 2004 bombing of the Moscow subway. Perhaps the most frightening, the deadly sarin gas attack on the Tokyo subway that send thousands to the hospital, and 12 to their grave. And then came 9.11. It drove the message home.

Along these rails, New York stands guard for danger. On a beautiful Indian summer morning, it struck from the most unlikely quarter. Right out of the clear blue sky, an unprecedented catastrophe has stopped the New York in its tracks.