It's funny how quickly everything changes. Thursday was one of those picture-perfect early autumn days when the bright, sunlit streets of New York were packed with people bustling along in post bank holiday back-to-school mode.
People had already decided how they were going to deal with looming 10th anniversary of 9/11 and everyone was in their own way prepared for the emotional overload, and inevitable tight security, that would kick in as part of this solemn occasion.
By Friday morning, as New Yorkers made their way to work through streets illuminated with the red-and-blue strobes of police cruisers, the vibe had changed. Even if you hadn't heard the news about the "credible" terrorist threat against the city, you could feel it -- a spooky mix of disbelief, confusion and barely muted dread.
Those who had decided to leave the TV off the night before purposefully tuning out the back-to-back pre-anniversary specials, couldn't avoid noticing what officials described as the increased police presence.
The pace of the city slowed to an unnatural crawl as commuters rubber-necked, watching cops pulling vans to the curb to check their contents. None of the drivers appeared to complain.
People smiled encouragement at the young cops wearing hard tin hats, with assault weapons strapped to their chests, who stood in tight groups of four at the subway entrance. And down in the tunnels nobody pretended to heed the ominously beady-eyed troops in camouflage fatigues patrolling the platforms.
By tea-time tables for baggage swabbing had been set up in many subway stations, while bomb-sniffing dogs marching along 42nd Street across Lexington and Fifth were a signal that the initiative to sweep public garages was under way.
Hubs like Grand Central and Penn stations were jammed with people eager to get home. Checkpoints at the midtown and Lincoln tunnels, the George Washington and Triborough Bridges snarled traffic as news filtered through that the terrorists' primary mission is to explode a car bomb in either New York or Washington.
According to one official, if that task proves too difficult, the terrorists are under orders to simply cause as much destruction as they can.
Mayor Bloomberg and police commissioner Kelly have been urging New Yorkers to go about their daily business as usual. In fact, they insist.
New Yorkers, of course, know the drill: stay calm and carry on or else the terrorists win.
And this morning, as the roll-call of the dead is ceremoniously read at Ground Zero, the city that never sleeps will sit upright in an unprecedented security lockdown united in the hope that commissioner Kelly had it right when he promised: "We have a lot on our plate -- but we have the talent and the resources to deal with it."