Boston ? It was a tame Halloween after all. The most popular costume on the market wasn’t a supervillain but an accidental superhero, Spider-Man. The small revelers on this death-defying holiday were dressed as angels. The witches and skeletons were as scary as stuffed animals.

Even the National Zoo in Washington bore a sign next to its haunted house: Do Not Be Afraid. And the trick-or-treaters were as threatening as a candy collection agency.

Well, I suppose the kids have had enough fear to go around this year. For weeks, there had been a boogeyman on the highways and on the news. Monsters had seemed far too real.

A sniper loomed over the landscape, growing in stature with every shooting. The analysts described him as a skilled marksman, a demonic genius, an intelligent and extraordinary serial killer. He declared himself “God” and warned, “Your children are not safe anywhere at any time.”

Then just before Halloween, two “demonic geniuses” were found sleeping at a highway rest stop.

How quickly reality deflates our fantasy figures. John Allen Muhammad turned out to be, in the words of a Washington Post story, a “serial loser.” Last week’s monster was “an archfiend, beast, devil, ghoul, ogre.” This week’s suspect is a strutting man of failed marriages and failed business ventures and failed fatherhood a loser with a young acolyte and a weapon.

This transformation seemed so familiar that I wonder why we create monsters to begin with. To match the monstrosity of the crime? Do we attribute some larger-than-life quality to people we fear and give powerful men the dark side of our respect? And why are we often surprised to discover that they are life-sized?

When the sniper suspects were caught, I remembered the day police broke into the Hamburg apartment where the terrorist, Mohamed Atta, had lived. All that remained of the Sept. 11 hijacker’s life were some eggshells and onion skins. The terrorist was a man who ate eggs and peeled onions. Did his eyes tear when he peeled them?

It’s not that sleeping makes snipers into ordinary folk, or that dining habits make terrorists kin to all the egg- and onion-eaters in the world. But such details brought the demons back to earth, planting them firmly at the table of the human species. Where, I am afraid, they belong.

Does this frighten us? Robert Precht, an assistant dean at the University of Michigan, is still “haunted” the word he chooses by the murderous clients that he represented in the 1993 World Trade Center bombings. You see, he says, “these were not programmed robots. These were not monsters.”

He remembers with wonder the day one of his murderous clients actually protested an unflattering profile in a local newspaper. It hurt the man’s feelings, outraged his sense of fairness. As Precht learned more about his clients’ background, families and motives, he says, “I was observing the evil and the human inexorably entwined.”

Questions about entwined humanity and monstrosity run deep through our culture. In the modern fables created for children, fear is often defanged.

The monsters in “Monsters, Inc.” are well-meaning workers misled into believing that the screams of children are needed for fuel. The ogre in “Shrek” is a slovenly loner who pre-empts his own expected rejection by vile behavior.

In the classic story for adults, even Frankenstein’s monster is not without some poignant glimmer of humanity. He was created and wants to connect with people, yet he can’t.

In real life, we know every serial killer is not a misunderstood child. Nor is every beast merely a waiting beauty. Maybe we resist “humanizing” a villain or a terrorist because we fear that understanding is accepting. We worry that recognizing the warped motives or the self-justifying ideology of a criminal would undermine justice.

But I also agree when Precht suggests that we turn sniper and terrorist into inhuman demons because “it is frightening to realize these people are not that different. It’s scary that they could be our neighbors, ourselves. We create these cartoons of evil to distance ourselves.”

Children ask “why.” Why did they fly the plane into the building? Why did they shoot those people at the gas station and the bus stop? Why?

As adults without answers, our instinct is to keep evil at arms’ length. But time and again, the costume comes off. We don’t find a monster, nor “God,” nor “the devil,” but a man who behaved monstrously.

When and why and how did another one of us cross the threshold? This question is the haunted house of our humanity.