Boston ? I turn on the news expecting the worst and I find it. Another girl has been abducted. This time the dateline is Missouri. This time the girl is 6-year-old Casey Williamson. And this time she’s been murdered.

Is this the season of fear? The summer of abductions? On June 5, Elizabeth Smart was taken from her bed in Salt Lake City at gunpoint, reawakening our slumbering terror of the stranger who comes after our children. Since then the names and the details have become all too familiar:

Five-year-old Samantha Runnion was playing Clue outside her Stanton, Calif., home when she was snatched, sexually assaulted and murdered. Seven-year-old Erica Pratt was taken from her Philadelphia row house to a basement where she managed, “miraculously,” to escape.

On TV, we see the anguish of the parents and the anger of the advocates. On one channel, Mark Klaas, whose daughter Polly was abducted in 1993, declares an “epidemic.” On another, a cable show host acts like a public health expert warning of a growing outbreak in the community.

And across the country parents seem to describe the same painful symptom: fear. “The world is more unsafe now,” says one mother. “I watch my 2-year-old more closely,” says another. “I won’t allow a stranger near my kids,” says a father.

Photos of missing children first began to appear on milk cartons in the 1970s. By the mid-1980s, New Jersey began to fingerprint school children. When Congress declared a National Missing Children’s Day, the media spread the alarming statistic that 1.5 million children were missing and 50,000 were abducted every year.

It took time for the facts to catch up to our darkest fantasies. Now we know that the vast majority of the missing are runaways and as many as 90 percent of the abducted are snatched by a parent fighting for custody. We know, too, that as “epidemics” came and went, the number of abductions by strangers hovered between 200 and 300 a year. The number of murders by strangers remained around 50 a year.

These were the figures in 1993 when Polly Klaas was murdered. They were the figures in 1994 when Susan Smith drowned her children and blamed it on a stranger. And in all the years before Elizabeth Smart’s disappearance started this “new outbreak.”

There is no way to exaggerate the pain of parents who have lost a child. No calculator was ever made that could overestimate the sum of their anguish. But it is possible to exaggerate the danger. And so it is worth asking why we are susceptible to this “epidemiology.”

David Finkelhor, a University of New Hampshire sociologist who studies crimes against children, says that this is an “archetypal” fear. It touches every parent who has ever lost sight of a toddler in a supermarket aisle or watched a first-grader bicycle off to school or waited and waited, and waited for a teenager to come home from the mall.

We may just be programmed to believe that someone from “another tribe” will come and steal our children. The terror of losing a child to strangers is, after all, a staple of old mythology and primal nightmares. Village folklore was full of tales of gypsies and vagrants. Even if there were only five such cases a year, says Finkelhor, it would touch a nerve. “You can’t talk people out of that with numbers.”

But today our “tribes” feel more fragile and our personal communities less stable. When we tell our children as we must to beware of strangers, there are more people who wear that label.

If our immune system is overwhelmed by this “epidemic,” it may also be because our children are routinely placed in the hands of strangers from doctors to teachers to day-caregivers. They are placed, as well, in the hands of television producers and Internet Web masters.

As Finkelhor suggests, “All our anxiety about feeling that we don’t have control over our children gets symbolically focused on the idea that someone is trying to take them from us.”

No, I don’t agree with the mother who says “the world is more unsafe now.” I remember polio. I remember growing up under the mushroom cloud of the Cold War. This year, terrorism expanded the repertoire of my imagination more than even the horrible tales of child abduction.

But as the images overwhelm the numbers, I notice how we identify and mourn with families we know only through television. Meanwhile, our neighbors become the strangers.

It isn’t child abduction that recycles in such overwhelming proportions. It’s fear. There is no epidemic of abduction by strangers. But there may be a contagious and chronic case of estrangement.