INTRODUCTION

On April 22, 2006, Kelly Lacek looked around her dinner table and smiled: Dan, her husband of thirteen years, was there, along with the couple's three children, Ashley, Stephen, and Matthew. Kelly's parents had also come over: There was a father-daughter dance at the local church that evening, and Kelly and her dad were double-dating with Dan and Ashley. As the four of them were getting ready to leave, Kelly couldn't resist needling her mother. "You're stuck with the boys," she said. "But don't worry--we won't be out too late." She kissed Stephen goodbye, and then bent down to say good night to Matthew. He was three years old, and Kelly marveled at how quickly he was growing up: It seemed as if it was only moments ago that he'd been an infant, and now he was already being toilet-trained. (Dan and Kelly both agreed that it was adorable how proudly he announced that he had to go to the bathroom.)

For a brief moment, Kelly says, she wondered if Matthew was okay--he seemed a little out of sorts, and earlier that afternoon, he'd complained of a sore throat--but then she figured he'd probably just tired himself out wrestling with his older brother.

Kelly and Dan returned home that night around eight o'clock. They'd barely walked in the door when Kelly's mother rushed over: "It's Matthew," she said. "He's running a fever--and his breathing seems a little shallow." The Laceks realized right away that something was seriously wrong. "He was just sort of hunched over," Kelly says. "We didn't know what to do." Since there was no way to get in touch with Matthew's doctor, they decided to make the ten-minute drive from their home in Monroeville, about fifteen miles east of Pittsburgh, to the Forbes Regional Campus of the Western Pennsylvania Hospital.

When the Laceks arrived at the emergency room, the attending physician told them there was nothing to worry about. In all likelihood, he said, Matthew had a case of strep throat. Worst-case scenario, it was asthma; regardless, they'd be home in no time. Two hours later, they were feeling much less assured: Matthew's fever was still rising, and when a doctor tried to swab his throat, he began to choke. By eleven p.m. Matthew's temperature had risen to 104 degrees and his breathing seemed to be growing shallower by the minute.

It was around that time that a doctor the Laceks hadn't met before walked over. He was older--probably in his sixties, Kelly thought--and as soon as he saw Matthew, he began to suck nervously on his teeth. He turned to the Laceks: Had Matthew received all his shots? Actually, Kelly said, he hadn't. Matthew had been born in March 2003, several years after rumors of a connection between autism and vaccines had begun to gain traction in suburban enclaves around the country. That May, Kelly's chiropractor warned her about the dangers of vaccines. "He asked if we were going to get [Matthew] vaccinated and I said yes," Kelly says. "And then he told me about mercury. He said, 'There's mercury in there.' " Kelly had already heard rumors that the combined measles-mumps-rubella (MMR) vaccine was dangerous, but this was something new. "He was really vocal about it causing autism. He said there was this big report over in Europe and blah blah blah. And I thought, Well, I'm surrounded by people who have autistic children. What if this happened to Matthew?" If Kelly was unconvinced, the chiropractor said, she should make Matthew's pediatrician prove to her that the vaccines Matthew was scheduled to receive were one hundred percent safe.

"So that's what I did," Kelly says. "I asked my doctor if she could give me a label that says there's no mercury and she said, 'No.' She...