I said into the radio, "Big Bird is mobile." I gave the make and color of the car and the plate number, and Unit Two acknowledged. Unit Two, by the way, is the second Dodge minivan, driven by a guy I know, Mel Jacobs, NYPD Intelligence Unit detective. Detective Jacobs is Jewish, and he speaks a little Hebrew, which he uses when interrogating Arabic-speaking suspects. That, and the Star of David that he wears, sends these guys into orbit, which is kind of funny to watch.

Anyway, the other guy with Mel today is George Foster, an FBI Special Agent who I've worked with and who I like because he knows from experience how brilliant I am.

The Mercedes headed north on Third Avenue, and Special Agent Sims asked me, "Should I follow him?"

"That might be a good idea."

She threw the SUV into gear and off we went, threading our way through heavy traffic. New York drivers are divided between the good and the dead. It's Darwinian. Ms. Sims would evolve or become extinct. And I'm sitting in the passenger seat to witness one or the other.

The Iranian chauffeur, who I think I've followed before, was an erratic driver, and I couldn't tell if he was driving like that to lose a tail or if he was just a really bad driver. Like the last thing he drove was a camel.

Meanwhile, Special Agent Sims had her chin over the steering wheel between white knuckles, and her right foot was moving from the brakes to the accelerator like she had restless leg syndrome.

The Mercedes made a sudden left on 51st Street and Ms. Sims followed.

Unit Two continued on Third where he'd hang a left on 53rd and run parallel to us until I could tell them what the Mercedes was doing. You don't want a parade following the subject vehicle; you want to mix it up a bit.

We were heading west now, and we passed beside St. Patrick's Cathedral, then crossed Fifth Avenue. The subject vehicle continued on, which I reported to Unit Two.

I had no idea where Big Bird was going, but he was heading toward the Theater District and Times Square, where these guys sometimes went to experience American culture, like strip joints and titty bars. I mean, you don't get much of that back in Sandland. Right?

The Mercedes made the light on Seventh Avenue, but we didn't and we got stuck behind three vehicles. I couldn't see the Mercedes now, but I had seen him continue on 51st. I hit the lights and siren, and the vehicles in front of us squeezed over, and Ms. Sims squeezed past and barreled through the red light, cutting across the southbound traffic on Seventh Avenue.

We got across the avenue, and I killed the lights and siren, and we continued west on 51st.

Ms. Sims glanced at me as though she wanted a compliment or something, so I mumbled, "Good driving."

I radioed Unit Two with our position and said, "I have subject vehicle in sight."

We drove through the area called Hell's Kitchen, formerly a nice slum, which has gone downhill with an influx of yuppies. I had no idea where Big Bird was going, but if he continued west, maybe he was headed for a Hudson River crossing. I said to Ms. Sims, "He may be going to Jersey."

She nodded.

In truth, ninety percent of our surveillances go nowhere. Abdul is just out and about, or he's trying to draw us off from something else that's happening. Or they're just practicing their countersurveillance techniques.

Now and then, though, you get the real thing-like one of these dips meeting a known bad guy. We do more watching than arresting or interrogating, because these characters can tell us more by keeping them under the eye than they'd tell us in an interrogation room. With the dips, you can't question them anyway, and getting them booted out is left to people with a higher pay grade than mine.

Now and then we do make an arrest, and I'm on the interrogation team, which is a lot more fun than following these clowns. I mean, I'm having fun; they're not.

The goal, of course, is to prevent another 9/11 or something worse. So far, so good. But it's been too quiet for too long. Like over a year and a half since that day. So, are we lucky, or are we good? For sure, the bad guys haven't given up, so we'll see.

The Mercedes continued on toward Twelfth Avenue, which runs along the Hudson River and is the place where civilization ends. No offense to New Jersey, but I haven't gotten my malaria shots this year.

I radioed Unit Two that we were traveling south on Twelfth.

There isn't as much traffic in this area of warehouses and piers, so the Mercedes picked up speed, and Ms. Sims kept up without being obvious.

The Mercedes passed the turns that would have led to the entrance of the Lincoln Tunnel and continued south toward Lower Manhattan.

Ms. Sims asked again, "Where do you think he's going?"

"Maybe one of the piers. Maybe he's got a rendezvous with a Saudi yacht that's carrying a nuclear device."

"Jeepers."

"Please don't swear."

"Shit."

"That's better."

We were making pretty good time down Twelfth Avenue, and I could see Unit Two in my sideview mirror, and we acknowledged visual contact. By now, the Iranian driver should know he was being followed, but these guys are so dumb they can't even find themselves in a mirror, let alone a tail.

Maybe I spoke too soon, because the guy suddenly slowed up, and Ms. Sims misjudged our relative speeds, and we were now too close to the Mercedes with no one between us and him. I could see Big Bird's head in the back right seat, and he was talking on his cell phone. Then the driver must have said something to him, and Big Bird twisted around in his seat, looked at us, then smiled and gave us the finger. I returned the salute. Prick.

Ms. Sims said, "Sorry," and dropped back.

I advised her, "You have to watch their brake lights."

"Right."

Well, it's not the end of the world when the subject is on to you. It happens about half the time when you're mobile, though less on foot.

There is a Plan B, however, and I called Unit Two and explained that we'd been burnt. I told Ms. Sims to drop farther back, and Unit Two passed us and picked up the visual tail.

We all continued on, and I kept Unit Two in sight.

I could have called for another surveillance vehicle, but the Iranians weren't doing any escape and evasion, so I just let it play out. They damned sure weren't going to lose us, and if I screwed up their plans today, that was a good day's work.

We got down below the West Village, and Unit Two radioed that the subject was turning on West Houston. Jacobs also said, "I think this guy made us."

"Then pull up alongside and give him the finger."

"Say again?"

"He flipped me the bird."

I heard laughter on the radio, then Unit Two said, "Subject is turning into the entrance ramp for the Holland."

"Copy."

In a few minutes, we were on the entrance ramp to the tunnel.

There are no toll booths in this direction so traffic was moving quickly into the tunnel entrance. I passed on a tidbit to Ms. Sims: "Almost none of these dip cars has E-ZPass-they don't want their movements recorded-so when there's a toll booth, they're in the cash lane, which is very slow, and if you go through the E-ZPass lane, you'll be ahead of them, which you don't want."

She nodded.

Unit Two was in the tunnel and we followed.

Inside the long tunnel, Ms. Sims asked again, "Where do you think he's going?"

This time I knew. "New Jersey." I explained, "That's where the tunnel goes."

She didn't respond to that bit of Zen, but she informed me, "Iranian diplomats may not travel more than a twenty-five-mile radius from Manhattan."

"Right." I think I knew that.

She had no further information for me, so we continued on in golden silence. The tunnels under the rivers around Manhattan Island are, of course, A-list targets for our Mideast friends, but I didn't think Big Bird was going to blow himself up in the tunnel. I mean, why put on such a nice suit for that? Plus, you need a big truck bomb to actually open the tunnel up to the river. Right?