Ben sheltered from the rain under one of the elegant porticos of the Blue Mosque, surrounded by scores of chattering tourists and keeping an oblique eye on the mosque's exit, fifty feet away. The Iranians had gone in ten minutes earlier, having walked from the hotel exactly as Ben had hoped. He knew from his earlier reconnaissance of the area that there was only one exit, so he hadn't followed them in.

The people around him conferred over their guidebooks in a dozen languages and snapped nonstop photos of the soaring minarets and massive semidomes and rows of ablution spigots. Ben kept his hat pulled low and the jacket zippered over his chin, his breath fogging before him. This wasn't an ideal place to do the job-it was too open, there were too many potential witnesses, it was too close to where he had been staying-but if an opportunity presented itself, he would take it, and he didn't want to be recognizable afterward in some idiot tourist's photos.

During their stroll from the hotel to the mosque, the scientists had showed no sign of security awareness. The VAVAK guys, though, were reasonably sharp. They had stayed one ahead and one behind the scientists, never letting the gap between their positions close to below twenty-five feet. Dropping one at point-blank range would mean having to engage the other from a distance, and possibly allowing the scientists to escape in the meantime. Going after the scientists first would mean giving the VAVAK guys an extra second to get their shit together and then an opportunity to engage from two different directions. The ideal was to drop all four almost instantly and walk away clean, and the VAVAK guys were naturally trying to make something like that as difficult as possible.

In addition to their tactical positioning, the VAVAK guys were also obviously surveillance conscious, but here they were operating at a disadvantage. Ben was pretty sure he knew their likely destinations-the major attractions of Sultanahmet and Seraglio Point-and their likely routes, so he could afford to lose visual contact from time to time. Also, the area was crowded with tourists, many of whom would be walking from one spot to the next in the same sequence the Iranians were following. Under the circumstances, multiple sightings of the same person wouldn't mean much. Toughest of all, about half the hundreds of people in the area were hunkering under black umbrellas and keeping their heads down against the chill and the rain, as Ben was, which made it hell to pick out individuals.

But Ben was operating under one significant disadvantage: he was alone, while the people he was using for concealment were mostly in pairs and groups. So from time to time he made sure to consult his own guidebook with studied fascination, to jot down some notes about the mosque's six minarets and turreted corner domes and special entrance for the sultan, to shoot a few photos, and to otherwise blend as much as he could with the tourists around him.

When the Iranians emerged, one of the scientists and one of the VAVAK guys headed down the steps and turned left while the other two remained under the portico. Ben instantly understood why they were splitting up: the scientist had to hit the head. He knew the restroom they were going to use, too, and it would have been ideal: small, secluded, at the bottom of a flight of stairs at the corner of the mosque grounds. But if something went wrong, he might come out of this with only half the job done, maybe less. No, better to wait for the right moment when he could catch them all closer together.

The scientist and the VAVAK guy returned after a few minutes, and Ben followed them to Hagia Sophia, waiting near the exit again while they were inside. Their next stop was Topkapi Palace, and this time one of the VAVAK guys waited outside. This confirmed for Ben what he already strongly suspected: the VAVAK guys were armed. Topkapi was home to a priceless collection of jewel-encrusted Ottoman swords and crowns and thrones, and there was a metal detector at the entrance to prevent anyone from bringing in hardware for a robbery. Ben figured the guy who was waiting was holding both their guns while the other accompanied the scientists inside. He was half tempted to hide the Glock somewhere and follow them in, but dropping all three barehanded would have presented something of a challenge. Not to mention all the cameras, the single point of egress, and the guards with submachine guns. No, there would be a better opportunity. He waited outside the massive palace gates, haggling with merchants, shooting a few photos, occasionally sneaking a peek through the entrance to make sure the VAVAK guy was still there. He watched the people coming and going carefully in case there was a countersurveillance unit involved. The intel hadn't mentioned it, but intel was never perfect and you had to be careful. He didn't see anything that rubbed him the wrong way.

After Topkapi, the Iranians headed west through the gathering dusk. Ben thought he knew where they were going: either the Grand Bazaar or the Spice Bazaar. If he was right, his opportunity was coming.

They wandered down narrow cobblestone streets through alternating pools of darkness and light, the sound of their footsteps echoing on the stone walls to either side and mingling with the conversation and laughter of shoppers and passersby What sky was visible was a dull, dying gray. The rain had stopped, but it was still humid and cold, and a sheen of perspiration gleamed on the peeling façades of souvenir shops and carpet stores and food stalls, all crammed side by side under sagging awnings and rusted escarpments. Ben kept well back, pausing when the Iranians paused, moving when they moved, staying cool, staying patient, knowing something would open up.

The sounds around them were suddenly drowned out by the evening muezzin chanting out the adhan, the call to prayer. Ben's Arabic wasn't as strong as his Farsi, but he understood the words:

God is greatest. I bear witness that there is no lord except God. I bear witness that Mohammed is the messenger of God. Make haste toward prayer. Make haste toward welfare. God is greatest. There is no lord except God.

The Iranians stopped at a small, undistinguished corner building recognizable as a mosque only from the minaret near its entrance. The scientists took off their shoes and went inside, accompanied by one of the VAVAK guys. The other waited outside. Ben smiled. Maybe they were willing to put their faith in God, but not their security. He hung back and waited.

Fifteen minutes later, they emerged and continued northwest. Come on, Ben thought. The Spice Bazaar. You know you want to.

They moved along Marpuccular Cad, the road that provided the southwest boundary of the bazaar, then onto Tahtakale Cad, still moving northwest. They paused from time to time to examine the wares of the various shops, but didn't go inside. The VAVAK guys maintained their tactical positions. Come on, Ben thought. Come on. Despite the cold he could feel himself perspiring.

He followed them right onto Uzunçarşi Cad, his breath starting to quicken slightly. It was full dark now. He'd been afraid they were going directly to the Galata Bridge, but now it looked good, it looked like it was the Spice Bazaar after all. He tightened the cords on the backpack and squeezed his left arm against the satisfying bulk of the holstered Glock.

He stayed with them until they turned right onto Hasircilar Cad, the main street of the Spice Bazaar. All right. This was what he'd been waiting for.

He turned and dashed down the middle of Tahtakale Cad, paralleling the route the Iranians were now on, dodging cars and trucks, staying off the sidewalks to avoid the thick clots of pedestrians. The backpack was secure. The weight of the Glock felt right.