We’ll get back shortly to more stories from people whose lives have been upended by having a family member’s name, photo, and address splashed up on a public sex offender registry. But to get at what’s behind America’s sex crime policies, it helps to understand the chilling events that got them rolling.

Start with an October Sunday evening in 1989 in the tiny Minnesota town of St. Joseph. Eleven-year-old Jacob Wetterling and his friend Aaron Larsen were babysitting Jacob’s kid brother and sister at the Wetterlings’ house. Jacob’s parents had gone to a dinner party in Clearwater, 20 miles away.

The boys were bored and wanted to ride their bikes to the Tom Thumb store a mile away to rent a movie. Getting permission would be a long shot—Jacob’s parents didn’t let their kids ride after dark. When 10-year-old Trevor Wetterling called his mother to ask permission, she said no.

But Trevor asked to talk to his dad Jerry. Trevor promised they’d take a flashlight. Aaron would wear a white sweatshirt. Jacob would wear his dad’s reflective vest. And he’d get a 14-year-old neighbor to babysit his 8-year-old sister Carmen while they were gone. So Jerry said yes—Jacob had had a rough day at hockey tryouts, and Jerry figured he needed to do something fun.

Jacob and Aaron took their bikes, and Trevor rode his scooter. They’d made a good decision on the flashlight—the moon wasn’t yet out and it was pitch-black out on the stretch of unlit country road they were traveling.

Halfway to the store, off on his left Aaron heard a rustle in the grass near the road. It could have been nothing, but it gave him a shiver. Something didn’t feel right. He sped up on his bike but kept silent.

They got to the Tom Thumb, picked out Naked Gun, and headed back. It was about 9:15. A half-mile from home, they were getting to the spot where Aaron had heard the noise when he saw something. A glint of metal.

Then a man stepped into the road and told them to stop. His voice was like the low growl of an angry pit bull. He was wearing a mask and all-black clothes. He said he had a gun. The boys hearts were racing, but Aaron thought it had to be a joke—a high-school kid playing a prank.

The man ordered them to turn off their flashlights and lie face-down in the ditch. Then, one by one, he had them turn over and tell him their ages. Trevor was first, and the man told him to run as fast as he could into the woods and not look back or he’d shoot. Next was Aaron, and the man told him to do the same.

As Aaron was starting to sprint, he saw the man grab Jacob by the arm. A hundred yards later, Aaron caught up with Trevor. They looked back. Jacob and the man were gone.

The two boys sprinted to the Wetterling house, and the babysitter’s father called the police shortly after 9:30. The cops raced to the scene and were there within 10 minutes of the call. They found three bikes lying on the road, tire tracks in a driveway where the boys had been taken, and Jacob’s footprints in the dirt. One was dug in—as if there’d been a struggle.

They blanketed the area with flashlights, had a bloodhound try to pick up the trail, and brought in a police chopper to flood the surrounding woods with light. No Jacob. No other clues.

In the days afterward, firefighters and volunteers combed the woods and fields. Local police brought in the FBI and National Guard search teams, who walked the area and followed up on leads. Photos of Jacob went up in stores and at truck stops throughout the Midwest.

Months and then a year passed. In 1990, the Wetterlings hired a private investigator to go to Amsterdam to track down a lead that Jacob had been seen at the airport there. The investigator came back empty. In the years since Jacob disappeared, police have followed 40,000 to 50,000 leads. And Jacob has never been found.

The kidnapper probably had a sexual motive. Child abductions by strangers are rare—there were 115 of them nationwide in 2002—that’s a hundredth of 1 percent of all missing children cases. But when they happen, about half involve sexual molestation or worse.

In Jacob’s case, the police had even more reason to think so. Ten months earlier, in the town of Cold Spring, 10 miles from St. Joseph, a 12-year-old boy named Jared had been walking home at night by himself from ice skating with friends. A man with a gun had stopped and forced him into his car.

The man molested him but released him within an hour. When he’d let Jared out of the car, he told him, “Don’t look back, or I’ll shoot.”

But in trying to find Jacob, the police were like biologists without a microscope—they lacked a critical tool.

The first 24 to 48 hours make or break a case in most police investigations. Cops have even less time in child kidnappings—when children are murdered, it usually happens within 3 hours of the abduction.

So to boost their chances of finding Jacob, cops needed a central database of offenders convicted of sex crimes against kids. That could have helped them quickly narrow the field of suspects and target those without alibis or whose movements that night made them possible perpetrators.

Patty and Jerry Wetterling launched a campaign for a new law that would give police just that. By July 1991, governor Arne Carlson had signed the Minnesota Sex Offender Registration Act passed, creating a computerized state database of offenders that cops could consult.

In turn, Minnesota’s law sparked a wave of similar laws in states across the country. By 1993, 39 states had them on the books.

Patty Wetterling wanted to go further. She started working with Minnesota Senator David Durenberger, who lived 8 miles away in St. Cloud, to craft a federal law that would require all states to set up such registries. It swept through Congress, and by September 1994, Bill Clinton had signed the Jacob Wetterling Crimes Against Children and Sexually Violent Offender Act.

All states now had to set up databases listing sex offenders and other offenders convicted of a small number of other crimes against minors, like kidnapping. It also covered those convicted of sexually violent offenses like rape, even if they didn’t involve minors. Offenders’ names were to stay in state databases for 10 years.

But Wetterling’s Congressional allies had carefully crafted the act. Only police could access the data in sex offender registries, not the public. (Though cops could tell the public about specific offenders who they thought posed special danger.) And the law excluded minors who had committed sex offenses from its coverage.

Events in New Jersey would soon change all of that.

Next week: How the Wetterling Act Got Hijacked