He decided to protest, if only to be noticed. He had to leave some evidence of his resistance.

As the plainclothes officer approached, Jonathan stood.

“You,” barked the policeman, pointing at Jonathan with his walkie-talkie. “Sit! Now!”

Jonathan started to push toward the aisle. He wouldn’t sit. He would fight. He knew he would lose, but that was beside the point.

“I said sit,” the policeman repeated. “Please, sir,” he added in a polite voice. “We’ll be off the aircraft in a minute. You’ll be able to leave then.”

Jonathan sank back into his seat as the column of policemen swept past. Turning his head, he watched as they confronted a clean-shaven African male seated in the last row of the economy cabin. The suspect protested, shaking his head, gesticulating wildly with his hands. There was a shout, a scuffle, a woman’s piercing scream, and then it was over. The man was out of his seat, hands raised above his head in a gesture of surrender.

Jonathan saw that he was a small man, bent as driftwood, wearing a heavy woolen sweater that was much too warm for the English summer. The suspect was speaking Swahili, or a dialect of Kikuyu. Jonathan didn’t need to understand the language to know that he was saying it was a mistake. He wasn’t the man they were looking for. Suddenly the accused reached for his bags in the overhead compartment. A uniformed police officer shouted and tackled him to the floor.

Moments later, the African was cuffed and led from the plane.

“I’ll bet he’s a terrorist,” said the elderly woman seated next to Jonathan. “Just look at him. It’s plain as day.”

“I wouldn’t know.”

“You can’t be too careful these days,” the woman added forcefully, lecturing her naive seatmate. “We’ve all got to keep a sharp eye. You never know who you’ll be sitting next to.”

Jonathan nodded in agreement.

It was called the Black Room, and it was one of five special operations centers manned by Her Majesty’s Immigration Service at London Heathrow Airport. BR4-Black Room Terminal 4-was located in a stuffy low-ceilinged office directly above the Terminal 4 arrivals hall. Immigration officers sat at a control board running the length of the room. A multiplex of video monitors was arrayed on the wall in front of them. Closed-circuit cameras positioned on the ceiling and hidden behind two-way mirrors focused on the travelers queuing for passport control. A wireless communications link connected BR4 with the passport inspectors on the floor.

As the world’s busiest airport, London Heathrow saw 68 million travelers pass through its gates each year, arriving from or en route to 180 destinations in Great Britain and abroad. Ten million of them counted as international arrivals, an average of 27,000 persons entering the country every day. It was the Immigration Service’s job to process these arrivals with an eye toward ferreting out those with a criminal bent and denying them entry into the United Kingdom.

Manipulating the closed-circuit cameras, the men and women seated at the control board proceeded systematically down their assigned queue, snapping photographs of each arriving passenger. The photograph was fed into Immigration Service’s proprietary facial recognition software and checked against a database of known offenders. In the event of a positive response, the suspect would be approached by one of the dozen or so undercover immigration officers scattered throughout the hall and guided to a private room, where he or she would be interrogated and a decision taken regarding his or her status.

The same cameras were equipped with a package of invasive scanners that measured a subject’s body temperature, heart rate, and respiration, as well as a still-classified imager capable of detecting facial tics for unconscious tell signs invisible to the naked eye. All the data was fed into a software program named MALINTENT that assessed with a 94 percent degree of accuracy whether the subject was harboring criminal intent.

“I’ve got a hot one,” said the officer manning post three.

A supervisor approached. “Who is it?”

The officer brought up an image of a Caucasian male with dark skin and close-cropped hair standing at the inspection booth. “Jonathan Ransom. American. Came in on Kenya Airways out of Nairobi.”

“How hot?”

“Temp’s running at ninety-nine comma five. Respiration elevated, with a heart rate of eighty-four. Facial indicators read plus six out of ten. Borderline malicious.”

“Is he on our books?”

A swipe of Ransom’s passport had sent the information contained on the travel document’s biometric security strip to the UK ’s domestic law enforcement database of wanted criminals or “persons of interest,” as well as similar databases maintained by Interpol, European Union member countries, the United States, Australia, Canada, and a dozen other countries friendly to the cause. “Nothing outstanding against in the UK.”

“And the States?”

“Still waiting.” Ransom’s name and passport number were then sent to the FBI’s national criminal database, where they were matched against a watch list containing the names of suspected terrorists, individuals with warrants outstanding, and anyone with a felony conviction.

“Looks like a decent bloke,” commented the supervisor as he studied Ransom’s image on the monitor. “Probably worked up because of that arrest on board. Who’d the CT boys take down, anyhow?”

CT stood for counterterrorism, of late the largest component of the London Metropolitan Police force, numbering some five thousand officers and support staff.

“Supposedly some Al-Qaeda supremo. A regional commander or something like that.” The officer did a double-take as the requested information began to stream in. “We’ve got something from Interpol. Ransom had a warrant issued for his capture six months back by the Swiss Federal Police.”

“What for?”

“Murder of two police officers. A bit strange, though. It says that the warrant was rescinded after six days.”

“That it?”

“‘No further information indicated,’” read the officer, swiveling in his chair and looking at his superior for further instructions.

“Patch me in,” said the supervisor, putting on a pair of headphones. “Let’s have a listen.”

The officer activated a microphone on the passport inspector’s jacket and an audio feed was delivered to the supervisor’s headphones.

“Dr. Ransom, is it, sir?” said the passport inspector with seeming disinterest. “Are you visiting the United Kingdom on business or pleasure?”

“I’m attending a medical conference at the Dorchester Hotel. I don’t know if that’s business or pleasure.”

“I’d say it qualifies as business. Will you be staying long?”

“Three days.”

“Not making any time for sightseeing?”

“Maybe on my next visit.”

“And you’ll remain in London for the duration?”

“At the Dorchester, yes.”

“What’s your next destination?”

“I’ll be returning to Kenya.”

“That your home, then?”

“For now.”

The inspector thumbed through the passport. “ Sierra Leone, Lebanon, Sudan, Bosnia, Switzerland.” He looked Jonathan in the eye. “Been a few places, haven’t you?”

“Wherever my work takes me.”

“What did you say you do?”

“I’m a physician.”

“The last one who makes house calls, by the look of it. Just a few more questions, sir, and then you’ll be free to go. Have you been feeling ill lately?”

Inside Black Room 4, the supervisor put down his headphones. “Anything from the Yanks?”

“Ransom’s on some kind of diplomatic list. If he boards a flight to the States, we’re to notify an agency in D.C. Gives a number here.”