At the Tenleytown Station, Duffy got off the train, and Theo followed him. Duffy walked quickly, as if he lived with the fear of being followed. After a few minutes, Theo lost him in a crowd. He called Chase, said he was waiting on the next train, and should be there in fifteen minutes.

Mr. Babcock was waiting at the Woodley Park Station, and he was not happy. Theo apologized repeatedly, fibbing that he had been caught in the crush of people and simply could not get off the train in time. Theo did not like the fact that he was being forced to lie. It was wrong and he tried to tell the truth at all times. However, occasionally he found himself in the awkward position of having to fudge on the truth for a good reason. On the subway, he had made the quick decision that it was more important to try and nail Pete Duffy than to get off when and where he was supposed to. If he got off with his classmates, Duffy would be gone, and a great chance to nail him would have been missed. Now, if he admitted to Mr. Babcock that he had deliberately stayed on the train, then all sorts of bad stuff would happen. He could not tell the truth about Pete Duffy, not now anyway, because he had no idea what to do with the truth. He needed some time alone to think things through.

He needed to talk to Uncle Ike.

For the moment, though, he was forced to apologize to Mr. Babcock, who was a nervous type to begin with. Back at the hotel, Mr. Babcock marched Theo over to Mr. Mount and made a full report of his student’s misdeed. As soon as Mr. Babcock walked away, Theo mumbled, “That guy just needs to relax.”

Mr. Mount, who trusted Theo and knew that if any kid could survive in the big city it was Theodore Boone, agreed and said, “Don’t do it again, okay? Just pay attention to where you are.”

“Sure,” Theo said. If you only knew.

Dinner was a pizza party in a hotel ballroom. Seating was not regulated; you could sit anywhere you wanted. So, typically, the boys took one side of the room and the girls the other. Theo nibbled on some crust and sipped water from a bottle, but his mind was not on pizza. He was certain he had seen Pete Duffy. He even remembered the way the man walked as he was entering and leaving the courthouse during his trial. It was the same walk. The same height and body type. Definitely the same eyes, nose, forehead, and chin. Theo had locked himself in his hotel bathroom and watched the video on his phone a dozen times.

Theo had found Pete Duffy! He still couldn’t believe it and he was still uncertain about what to do next, but in his excitement he had almost forgotten something important. Since Duffy had fled town, the police had posted a $100,000 reward for information leading to his arrest and conviction. In his room before dinner, Theo had gone online and verified this reward. The Strattenburg police website had several pages dedicated to the Duffy case. There were several close-up photos of his face.

Cell phones were strictly prohibited during meals — if one was seen by an adult it was to be immediately confiscated. Halfway through the pizza party, Theo informed Mr. Mount that he needed to walk down the hallway to the restroom. Once inside, Theo locked himself in a stall and called Ike.

“I thought you were in Washington,” Ike said.

“I am. Ike, I saw Pete Duffy on the Metro. I know it’s him.”

“I thought he was in Cambodia or some place.”

“Not now. He’s right here in Washington. I got him on video. I’ll e-mail it to you right now. Take a look and I’ll call you later.”

“You’re serious, aren’t you?” Ike said, his voice suddenly sharper.

“Dead serious. Later.” Theo quickly e-mailed the video to Ike, then left the restroom and hustled back to the ballroom.

After dinner, when it was dark, the entire eighth grade loaded onto the four buses and headed for the Lincoln Memorial. There, they milled about the famous statue of Lincoln sitting and staring seriously — did the guy ever smile? Theo wondered — while clutching the sides of his chair. The lights cast even more shadows on his face, and Theo found it all quite awesome. With the assistance of a park ranger, Mr. Babcock, who evidently was a big Lincoln fan, set up a large screen at the foot of the steps — fifty-eight steps to be exact — and the students gathered around for a quick lecture. They listened in perfect silence as Mr. Babcock recapped the significant events of Lincoln’s life, material they had all covered in class, which now meant much more sitting on the steps of his memorial. As he spoke, Mr. Babcock, who was a compelling teacher, flashed photos of Lincoln as he advanced through his life.

Though the students were sitting on marble steps, there was no wiggling and no whispering. They absorbed the lecture with great interest. When Theo looked away, he gazed upon the awesome sight of the Reflecting Pool just in front of them. Beyond it, a mile away, was the towering Washington Monument, also lit to perfection. And beyond that, another mile away, was the US Capitol, its dome glowing magnificently in the night. When Theo turned around, he found President Lincoln staring down at them.

Theo knew it was a moment he would never forget.

They gave Mr. Babcock a round of applause when he finished. Next up was Ms. Greenwood, a popular African American lady who taught English to the girls. She began by asking the students to look all the way down to the Washington Monument and to try to imagine the Mall packed with almost a quarter of a million people. The day was August 28, 1963, and black people from all over America had marched on Washington to demand justice and equality. They were led by a young Baptist minister from Atlanta named Dr. Martin Luther King Jr.

As she spoke, she flashed images onto the screen, photos of the crowd that day, of people marching and carrying signs. She explained that Dr. King delivered one of the most famous speeches in American history, right over there on a temporary podium, under the proud gaze of the president who ended slavery. She then played a tape of the speech, black-and-white footage of Dr. King and his dream.

Theo had seen and heard the speech before, but it was far more moving at that moment. As Dr. King’s words echoed through the night, Theo looked down the Mall and tried to imagine what it was like that day, with thousands of people packed together and listening to words that would live forever.

They applauded for Ms. Greenwood, too, when she finished. Mr. Mount said there would be no more lectures. The students were allowed to hang around the Reflecting Pool for an hour or so. Theo found a seat on a park bench and texted Ike: Did you get video? What do you think?

Evidently, Ike was waiting: I’d say it’s p duffy. Let’s talk.

Okay. Later.

Later, at the hotel, as his three roommates were watching television and waiting on the ‘lights-out’ order from Mr. Mount, Theo went to the bathroom, locked the door, and took a seat on the toilet. He called Ike, who again seemed to be waiting with the phone in his hand. He asked, “Have you told anyone?”

“Of course not,” Theo said. “No one but you. What are we going to do?”

“I’ve been thinking and I have a plan. I’ll catch an early flight to DC and land at National around noon. I want to be on the subway when he gets on this afternoon and follow him as closely as I can. I need the time, the station, and the Metro line.”

Theo had already taken notes and had it memorized. “It’s the Red Line. We got on at the Metro Center Station, and I’m positive he was already on the train.”

“How many cars on the train?”

“Uh, just guessing, I would say seven or eight.”

“And which car did you get in?”

“Don’t know, but somewhere close to the middle.”