American comics: I am full of martial virtues and I love to be kind to others.

His mind was racing, piecing together various clues in his head.

“They’re ignored,” Lynn said, his voice growing increasingly certain. “There’s a type of person in the city who’s completely ignored. Nobody remembers their face, nobody cares where they go or what they do. They can appear anywhere without arousing suspicion. They’re like part of the urban landscape—”

“A homeless man!” Sarah exclaimed in realization.

“Yes! Homeless people!” Lynn exclaimed excitedly, but the movement aggravated his wound, causing him to wince in pain. “Think about it, homeless people can wander anywhere and go unnoticed. They can loiter near construction sites, sleep in parking lots, sit on park benches all day. Nobody will ask them why they’re there, nobody will remember their faces.”

“And the surveillance cameras don’t really focus on them,” Sarah continued, her train of thought echoing, “When we review the footage, we usually filter out people who seem irrelevant, and homeless people are often categorized as background noise.”

“Exactly,” Lynn said. “If the killer disguises himself as a homeless person, he can investigate, prepare, and even observe the outcome near the crime scene without attracting any attention. It’s the perfect disguise.”

“But that’s just speculation,” Sarah cautioned. “We need evidence.”

“Then let’s find evidence,” Lynn said, getting out of bed. “Retrieve all the surveillance footage from around the crime scenes, not just looking at suspicious individuals, but specifically targeting homeless people. See if the same homeless person appears at multiple crime scenes.”

"Lynn, your injury—"

“It’s okay, I can walk,” Lynn said stubbornly, though every step made him want to cry out in pain. “This might be the first time we’ve really gotten close to the killer. I can’t lie here.”

Sarah knew that persuasion was useless, so she could only support him and help him put on his clothes. The doctor came over to stop them, but Lynn showed his FBI badge, claimed it was an emergency, and signed the discharge papers.

An hour later, Lynn and Sarah returned to the FBI office. Despite the physical pain, Lynn was unusually excited. He felt he had finally found a breakthrough.

“Summon all the technicians,” Lynn told Sarah. “I need them to pull up all the CCTV footage from the areas surrounding the incident sites over the past two weeks. The timeframe is from three days before the explosions to one day after.”

“Understood,” Sarah began making the call.

Soon, a temporary working group was formed. Six technical analysts gathered in the conference room, in front of multiple computer monitors displaying surveillance footage from various locations.

“What are we looking for?” a young technician asked.

“Homeless,” Lynn said, “anyone who looks like a homeless person. Ragged clothes, a backpack, maybe pushing a shopping cart, maybe sleeping on the street. Record the time and place of every homeless person's appearance, then we compare them to see if the same person appeared at multiple crime scenes.”

“This is a huge workload,” the technical lead said. “The number of homeless people in New York—”

“I know,” Lynn interrupted him, “but this is our best lead. Let’s get to work.”

For the next five hours, the office was a hive of activity. Technicians meticulously reviewed each segment of surveillance footage, using software to tag every figure resembling a homeless person. They recorded the time, location, and physical characteristics to build a database.

Lynn sat to the side, his physical pain making it difficult to concentrate, but he forced himself to stay awake and oversee the process. Sarah brought him coffee and painkillers, but he only drank the coffee and refused the painkillers—he needed to keep his mind clear.

At 10 p.m., the first comparison result came out.

“Agent Holt, look at this,” a technician said, projecting an image onto the large screen. “The Brooklyn abandoned warehouse bombing: a homeless man was seen in the vicinity three times two days before the incident.”

The screen showed a disheveled man wearing a dirty, worn-out military jacket and a tattered beanie, pushing a shopping cart full of odds and ends. His face was mostly obscured by the hat and unkempt beard, but he appeared to be a white male of medium build.

“Continue,” Lynn said.

"Queens construction site bombing," the technician switched to another video clip, "The day before the incident, a homeless man, possibly the same person, was seen loitering outside the construction site fence."

The video quality was even worse this time, but a similar figure could indeed be seen—the same jacket, the same beanie, the same shopping cart.

"The Manhattan parking lot bombing," the technician continued, "was it this person again on the morning of the incident."

More and more evidence appeared on the screen. Although the angles and lighting were different each time, and although the person seemed to be deliberately avoiding the camera, technicians confirmed through body shape, gait, and the distinctive shopping cart that it was very likely the same person.

"There were five crime scenes in total, and this homeless man appeared at four of them," the technical director concluded. "Statistically speaking, this is unlikely to be a coincidence."

"And the fifth one?" Lynn asked. "The one at the stadium?"

“We’re investigating,” another technician said. “The stadium’s surveillance system is more complex and will take more time.”

“And last night’s,” Sarah added, “that apartment building in Brooklyn.”

“We’re investigating that too,” the technician said.

Lynn stood up, walked to the large screen, and carefully observed the image of the homeless man. Although he couldn't see his face clearly, he could sense that this was the person he was looking for.

“Can you enhance the image?” Lynn asked. “I need to see his face more clearly.”

“We can try, but the video quality is very poor, and he kept his head down the whole time,” the technician said. “We’ll use software to process it and see if we can get a clearer image.”

Another hour of waiting ensued. Technicians used various software programs to adjust contrast, reduce noise, and attempt to reconstruct the obscured facial features.

Ultimately, they obtained several relatively clear images. Although still not very clear, some basic features could at least be discerned: a white male, approximately thirty to forty years old, with dark hair, a beard, a high nose bridge, and a slightly pointed chin.

“We input these features into the facial recognition system,” Lynn said, “and compare them with driver’s license databases, passport databases, and criminal record databases.”

“It’s already being processed,” the technical lead said, “but given the image quality, the match may not be very accurate.”

“Just do your best,” Lynn said.

Just then, the technician responsible for reviewing the stadium's surveillance footage suddenly exclaimed, "Found it! The stadium, the stadium from the day of the incident!"

Everyone's attention immediately focused on his screen.

"This homeless man appeared outside the stadium three hours before the match started," the technician said, playing video footage. "He loitered around the parking lot for a while, and then...look, he approached the players' entrance."

The video shows the homeless man pushing a shopping cart slowly approaching a side entrance of the stadium—the one used by players and staff. A security guard came out, seemingly to shoo him away, but the homeless man pulled something out of his pocket and showed it to the guard. The guard looked at it, then let him in.

“Enlarge that part,” Lynn said.

The technician zoomed in on what the homeless man had handed to the security guard. Although the image was blurry, it was clear it was some kind of identification. "A staff ID?" Sarah guessed.

“Or forged documents,” Lynn said. “He could have gone in disguise as a maintenance worker or something. That would explain how he put the bomb in the break room.”

“What about last night?” Sarah asked.

“Still investigating,” the technician said, his fingers flying across the keyboard.

Ten minutes later, the results came out.

“The apartment building at 337 Green Street, Brooklyn,” the technician said. “An hour before the incident, this homeless man was seen on the nearby streets. He loitered around for about twenty minutes, then walked towards the apartment building, and then he disappeared from the surveillance footage.”

“But half an hour later,” the technician switched to another angle, “he reappeared, having left that area. Notice his shopping cart—it went in full, but came out with some items missing.”

“Those things might have included bomb-making materials,” Lynn said. “He took them into the apartment, assembled them, and then left.”

The evidence is piling up and becoming increasingly clear. This person, disguised as a homeless man, is almost certainly the perpetrator of the serial bombings.

“The problem now is, how do we find him?” Sarah asked.

“Set up surveillance,” Lynn said. “Since he’s already been to six locations, he might reappear. Have all patrol officers look for homeless men matching this description—white males wearing military jackets, beanies, and pushing shopping carts. But don’t disturb him; report it immediately if you spot him.”

“There’s another question,” the tech lead said. “If he’s just pretending to be homeless, what’s his real identity? Where does he live? What does he do in his daily life?”

“This is what we need to find,” Lynn said. “Are the facial recognition results in yet?”

"It's being processed and will probably take another half hour," the technician said.

Lynn glanced at the clock on the wall; it was nearly midnight. He felt a wave of dizziness; his injuries and exhaustion were beginning to take over. But he couldn't stop; he couldn't give up so close to the truth.

“Give me a strong coffee,” he said to Sarah. “And tell Captain Reynolds to send men to every homeless shelter in New York City and ask the staff if they’ve seen anyone matching this description. The killer might have actually been in a shelter to learn how to perfectly impersonate a homeless person.”

“Understood,” Sarah began making the call.

Lynn walked to the window and looked out at the night sky. The lights of Manhattan twinkled; this city that never sleeps is vibrant even in the dead of night. Among its eight million inhabitants, somewhere, a murderer is planning his next attack.

But now, Lynn finally saw his shadow.

This ghostly killer had always been in the most conspicuous place—so conspicuous that everyone overlooked him.

“Clever,” Lynn said softly, “but not clever enough. You left traces, and I found them.”

He turned and went back to the conference room to wait for the facial recognition results. Although he was in excruciating pain and exhausted to the point of collapse, Lynn's eyes burned with determination.

The manhunt is not over yet, but the scales are beginning to tip.

The murderer may not yet know that his "perfect disguise" has been exposed.

Lynn Hall will not give him a second chance.

Half an hour later, the facial recognition system provided the results.

“We found seventeen possible matches,” the technician said, “with similarities ranging from 62% to 81%. I sorted them by similarity.”

Seventeen driver's license photos and corresponding personal information were displayed on the screen. Lynn examined them one by one, looking for any suspicious clues.

Most of them are ordinary citizens—teachers, accountants, technicians, and salespeople. They have no criminal record and no obvious motive.

But Lynn stopped when he saw the fourth match.

The photo shows a 35-year-old white male named Richard Sanders. His occupation is listed as "historian." His address is in Brooklyn.

“Get his detailed information,” Lynn said.

More information appears on the screen. Richard Sanders, PhD in History from Columbia University, specializing in "historical cycle theory and social repetitive patterns," resigned from the university five years ago and has had little record since.

“History,” Lynn said softly, “remember history, history repeats itself. That was his motive.”

“You think it’s him?” Sarah asked.

"The similarity is 79%, the professional background and case messages match perfectly, and he suddenly disappeared from normal life five years ago," Lynn listed the evidence. "There are too many coincidences. Let's go to his address and take a look."

“Now, Lynn, it’s already past midnight, and your injury—”

“Now,” Lynn said firmly. “If he really is the murderer, we can’t give him any chance to escape or act again.”

At 2 a.m., three black SUVs were parked silently at the end of a dimly lit street in Brooklyn. Inside were eight agents from an FBI tactical team, along with Lynn, Sarah, and Captain Reynolds.

Richard Sanders' address is an old, three-story apartment building on a quiet street in the Sunset Park district. The area, formerly industrial, is gradually being converted into residential housing, but retains a somewhat dilapidated atmosphere.

"The target building is fifty meters ahead," the tactical team leader, a burly man named Marcus, whispered through his headset. "There's a faint light in the right-hand window on the second floor; the other windows are dark."

Lynn observed the target building through night-vision binoculars. It was an old red-brick building with fire escape staircases, appearing to be at least seventy years old. Sanders' apartment was on the second floor, and a sliver of light was indeed shining through the window.

“Someone’s home,” Lynn said. “Or maybe he left a light on.”

“Thermal imaging shows a heat source on the second floor, possibly a person,” another technical agent reported, “but it’s impossible to determine if it’s our target; it could just be a heater or another heat source.”

“Building structure?” Lynn asked.

“A standard old-fashioned apartment building layout, with an exit at the front and back, and a fire escape leading to the back alley,” Marcus said, unfolding the building's floor plan. “If the target were trying to escape, the most likely route would be the fire escape or the back door.” (End of Chapter)