The most intriguing candidate for that "something else" is called the Broken Windows theory. Broken Windows was the brainchild of the criminologists James Q. Wilson and George Kelling. Wilson and Kelling argued that crime is the inevitable result of disorder. If a window is broken and left unprepared, people walking by will conclude that no one cares and no one is in charge. Soon, more windows will be broken, and the sense of anarchy will spread from the building to the street on which it faces, sending a signal that anything goes. In a city, relatively minor problems like graffiti, public disorder, and aggressive panhandling, they write, are all the equivalent of broken windows, invitations to more serious crimes:

Muggers and robbers, whether opportunistic or professional, believe they reduce their chances of being caught or even identified if they operate on streets where potential victims are already intimidated by prevailing conditions. If the neighborhood cannot keep a bothersome panhandler from annoying passersby, the thief may reason, it is even less likely to call the police to identify a potential mugger or to interfere if the mugging actually takes place.

This is an epidemic theory of crime. It says that crime is contagious — just as a fashion trend is contagious — that it can start with a broken window and spread to an entire community. The Tipping Point in this epidemic, though, isn't a particular kind of person — a Connector like Lois Weisberg or a Maven like Mark Alpert. It's something physical like graffiti. The impetus to engage in a certain kind of behavior is not coming from a certain kind of person but from a feature of the environment.

In the mid-1980s Kelling was hired by the New York Transit Authority as a consultant, and he urged them to put the Broken Windows theory into practice. They obliged, bringing in a new subway director by the name of David Gunn to oversee a multibillion-dollar rebuilding of the subway system. Many subway advocates, at the time, told Gunn not to worry about graffiti, to locus on the larger questions of crime and subway reliability, and it seemed like reasonable advice. Worrying about graffiti at a time when the entire system was close to collapse seems as pointless as scrubbing the decks of the Titanic as it headed toward the icebergs. But Gunn insisted. "The graffiti was symbolic of the collapse of the system," he says. "When you looked at the process of rebuilding the organization and morale, you had to win the battle against graffiti. Without winning that battle, all the management reforms and physical changes just weren't going to happen. We were about to put out new trains that were worth about ten million bucks apiece, and unless we did something to protect them, we knew just what would happen. They, would last one day and then they would be vandalized."

Gunn drew up a new management structure and a precise set of goals and timetables aimed at cleaning the system line by line, train by train. He started with the number seven train that connects Queens to midtown Manhattan, and began experimenting with new techniques to clean off the paint. On stainless-steel cars, solvents were used. On the painted cars, the graffiti were simply painted over. Gunn made it a rule that there should be no retreat, that once a car was "reclaimed" it should never be allowed to be vandalized again. "We were religious about it," Gunn said. At the end of the number one line in the Bronx, where the trains stop before turning around and going back to Manhattan, Gunn set up a cleaning station. If a car came in with graffiti, the graffiti had to be removed during the changeover, or the car was removed from service. "Dirty" cars, which hadn't yet been cleansed of graffiti, were never to be mixed with "clean" cars. The idea was to send an unambiguous message to the vandals themselves.

"We had a yard up in Harlem on one hundred thirty-fifth Street where the trains would lay up over night," Gunn said. "The kids would come the first night and palm the side of the train white. Then they would come the next night, after it was dry, and draw the outline. Then they would come the third night and color it in. It was a three-day job. We knew the kids would be working on one of the dirty trains, and what we would do is wait for them to finish their mural. Then we'd walk over with rollers and paint it over. The kids would be in tears, but we'd just be going up and down, up and down. It was a message to them. If you want to spend three nights of your time vandalizing a train, fine. But it's never going to see the light of day."

Gunn's graffiti cleanup took from 1984 to 1990. At that point, the Transit Authority hired William Bratton to head the transit police, and the second stage of the reclamation of the subway system began. Bratton was, like Gunn, a disciple of Broken Windows. He describes Kelling, in tact, as his intellectual mentor, and so his first step as police chief was as seemingly quixotic as Gunn's. With felonies — serious crimes — on the subway system at an all-time high, Bratton decided to crack down on fare-beating. Why? Because he believed that, like graffiti, farebeating could be a signal, a small expression of disorder that invited much more serious crimes. An estimated 170,000 people a day were entering the system, by one route or another, without paying a token. Some were kids, who simply jumped over the turnstiles. Others would lean backward on the turnstiles and force their way through. And once one or two or three people began cheating the system, other people — who might never otherwise have considered evading the law — would join in, reasoning that if some people weren't going to pay, they shouldn't either, and the problem would snowball. The problem was exacerbated by the fact fare-beating was not easy to fight. Because there was only $1.25 at stake, the transit police didn't feel it was worth their time to pursue it, particularly when there were plenty of more serious crimes happening down on the platform and in the trains.

Bratton is a colorful, charismatic man, a born leader, and he quickly made his presence felt. His wife stayed behind in Boston, so he was free to work long hours, and he would roam the city on the subway at night, getting a sense of what the problems were and how best to fight them. First, he picked stations where fare-beating was the biggest problem, and put as many as ten policemen in plainclothes at the turnstiles. The team would nab farebeaters one by one, handcuff them, and leave them standing, in a daisy chain, on the platform until they had a "full catch." The idea was to signal, as publicly as possible, that the transit police were now serious about cracking down on fare-beaters. Previously, police officers had been wary of pursuing fare-beaters because the arrest, the trip to the station house, the filling out of necessary forms, and the waiting for those forms to be processed took an entire day — all for a crime that usually merited no more than a slap on the wrist. Bratton retrofitted a city bus and turned it into a rolling station house, with its own fax machines, phones, holding pen, and fingerprinting facilities. Soon the turnaround time on an arrest was down to an hour. Bratton also insisted that a check be run on all those arrested. Sure enough, one out of seven arrestees had an outstanding warrant for a previous crime, and one out of twenty was carrying a weapon of some sort. Suddenly it wasn't hard to convince police officers that tackling fare-beating made sense. "For the cops it was a bonanza," Bratton writes. "Every arrest was like opening a box of Cracker Jack. What kind of toy am I going to get? Got a gun? Got a knife? Got a warrant? Do we have a murderer here… After a while the bad guys wised up and began to leave their weapons home and pay their fares." Under Bratton, the number of ejections from subway stations — for drunkenness, or improper behavior — tripled within his first few months in office. Arrests for misdemeanors, for the kind of minor offenses that had gone unnoticed in the past, went up fivefold between 1990 and 1994. Bratton turned the transit police into an organization focused on the smallest infractions, on the details of life underground.