What I remember most is running. It was just after 3 p.m., German time, and I was tearing through the exhibition hall at the Frankfurt auto show, unable to find a TV.

The initial report was sketchy. A reporter friend from USA Today had texted me about a small plane crashing into the World Trade Center. When his next message mentioned a second plane, I took off.

In the media room, writers were still fashioning articles about the new Fords. I raced back to the hotel. There, my USA Today friend said presciently, "Somehow, everything we do for the next couple of years will have to do with today."

He spent most of the next few years in Afghanistan. And I was sent all over Europe and North Africa, chasing shadows.

Two days after the 9/11 attacks, the news broke that the lead suicide pilot, Mohamed Atta, had been living two hours away, in Hamburg. Suddenly I was on the biggest police story of my life.

On the train, a woman watched me as I read the International Herald Tribune. American? she asked. When I nodded, she grabbed my hand.

"We have to be strong," she said, repeating her words in beautiful, heavily accented English. She looked to be in her 70s. She laid out a multifront strategy for fighting extremism, urging vigilance, patience, and sensitivity, and I felt I was being welcomed into the world's arms.

The Germans had lived through terror attacks by the Red Army Faction. The French had withstood subway bombings by Algerian militants. The Brits had the IRA, the Spanish had ETA. Americans were exceptional no more. The world, she assured me, was with us.

In Hamburg, we learned that Atta and two of the other pilots had shared a three-room, furnished apartment with a high-speed Internet connection on Marienstrasse, near the technical university in a neighborhood of transients: students and immigrants.

I found Atta's academic adviser, who talked of the serious, rigid scholar who'd written an excellent thesis on urban planning in Aleppo, Syria. Later, a Moroccan student who knew the perpetrators told me he was shocked to hear what they'd done. Turns out he'd trained for jihad, too, and is now in prison, an accessory to murder.

A colleague reached a hausfrau who said that every night, when she cooked an egg for her husband, she looked out the window at Atta's apartment and the silhouetted members of his cell meeting behind drawn curtains.

Al-Qaeda in her backyard.

Across Europe, I felt embraced. France's Le Monde ran an editorial, "We are all Americans." Berlin police parked a tank outside the German American school where my wife taught, and police officers protected their allies with automatic weapons.

My editors were based in Washington, and they had good intelligence. Despite what my European friends thought, I knew the Bush administration was intent on war with Saddam Hussein and America was pulling away from the world.

The signature exchange for me took place in a Munich hotel, at a 2003 security conference, where Joschka Fischer, Germany's foreign minister, challenged the United States' case for invading Iraq.

"Excuse me, I am not convinced," he said, peering over his reading glasses as Donald Rumsfeld, U.S. secretary of defense, sat behind a potted plant sipping water, a tiger in the grass.

By then the anti-American rallies had started. The looks. The lectures. My children were careful when speaking English on the bus.

Back in the United States, we felt just as dislocated. During summer leave, we visited friends at the beach in Delaware and were overwhelmed by the scale of everything - the muffins, the people, the Hummers. Where was the urgency, the shared sacrifice?

Ten years after, one moment sticks out. We're in a rental car, and two lanes of traffic are narrowing into one. We wait our turn, orderly like Old Europe, and a giant SUV jumps the line. I give the horn a quick toot and notice the cute kid in the car in front of us. He is giving us the finger. We'd returned to another country.