“Detective Inspector Sanderson, Stockholm police. I’m here on urgent business.”

“One minute.”

Expecting the door to open any second, Sanderson reached into his overcoat for what he’d snatched out of his desk yesterday. Years earlier he’d taken a summer posting as a liaison officer to Interpol, a relatively pleasant three months in Lyon, France, in which he sorted through the felons of greater Europe. On returning to Stockholm, Sanderson realized that he’d not surrendered his Interpol credentials before leaving, and with little thought had simply shoved them into a desk drawer. The document, of course, had long ago lapsed, but the small print of the expiration date left virtually no chance of this being noticed. And like all policemen, Sanderson knew that when it came to establishing authority, attitude and volume were far more persuasive than paper and ink.

So it was, when the door opened moments later he flashed his old ID at the security guard and barged ahead, barking, “I have to identify all aircraft that were over the city yesterday at midday. Who must I talk to?”

A clearly flummoxed guard said, “That would be the air traffic manager, sir.”

“Well don’t just stand there with your mouth hanging open, get him!”

*   *   *

Minutes later Sanderson was talking to a very capable woman named Rolf.

“We keep records for a running sixty-day period,” she explained. “After that everything rolls into a long-term storage database.”

Rolf led him to a dark room where air traffic controllers were busy behind workstations. All wore headsets, and their faces were illuminated by multicolored displays as they guided aircraft with chattering instructions.

“What time yesterday are you concerned with?” she asked.

“Eleven thirty-two in the morning.”

She looked at him questioningly, then began typing at a vacant console. “And you’re looking for an aircraft that was over the city?”

“That’s right.”

The screen in front of them blinked to life, and then settled to a black map display that was highlighted with concentric arcs and lines. Seconds later, this background was overlaid with scattered alphanumeric symbols.

“I see six aircraft over the city.” She pointed to a pair of white squares that were tagged with data blocks. “These two are airliners. They are at high altitude and moving fast.”

“No, I’m looking for something else. An aircraft that stayed over the city for a period of twenty or thirty minutes.”

Rolf tinkered with the display, going forward and back in time until her finger settled on one square. “This one. It was circling the downtown area for thirty minutes, very low and slow. I’m not sure why—nobody would have been sightseeing given yesterday’s weather.”

“No, they wouldn’t,” Sanderson agreed. “What kind of airplane was it?”

“A Cessna,” she replied.

“Where did it go next?”