Then, last month, she became absorbed in a different book. This time the experience was considerably less pleasant.

The book was “Harriet the Spy,” a novel of such sustained popularity that it can be considered a classic. It was a book I had loved as a child, and reading it to my daughter now, I relived my earlier pleasure in the spunky and resilient Harriet, the betrayal she feels when her friends read her diary and the hard lesson she learns about becoming a better friend and a more compassionate person. But some parts of the novel had not aged particularly well. Revisiting the book now, I paused on page 29 when Harriet’s best friend, Janie Gibbs, a novice scientist with a home laboratory full of simmering potions, is introduced with the words, “She had a chemistry set and planned one day to blow up the world.” Wow, I thought. You certainly couldn’t write that today–not after Jonesboro, Paducah, Columbine. Poor Janie Gibbs would be in custody the first time she announced her cataclysmic intentions, and her parents right behind her!

Within days my daughter announced her intention to blow up a classmate’s house. She did this infused with the image of Janie Gibbs’s chortling away at her beakers and Bunsen burners, but my daughter’s classmate was not as impressed as Harriet: she was terrified. So were her parents, who called the school, and the teachers, who called a meeting. Did my husband and I know that our daughter was talking about setting off a bomb?

In the days after Columbine, while many of my friends were asking how Dylan Klebold’s and Eric Harris’s parents could not have known their sons were about to visit such destruction on their community, I was quietly worrying whether one of my children might ever be able to metamorphose into a mass murderer without my noticing. After all, both the Harrises and the Klebolds seemed like normal people, not so very–dare I say it?–unlike myself. Indeed, in their maudlin, post-mortem videos, the two murderers seemed to go out of their way to absolve their parents of associative guilt by crowing “They don’t have a clue!”

But when I confessed this fear to one of my friends, she shook her head. “Don’t you think you’d notice if your child started wearing swastikas to school?”

Or talking about setting off a bomb?

I could imagine the enraged headlines: 7-YEAR-OLD THREATENED HER CLASSMATE WITH A BOMB AND THE PARENTS LAUGHED IT OFF!

The thing was, I really had felt like laughing when my daughter’s teachers had, with dread and horror in their voices, revealed the reason they had asked to meet with us. Come on… “Harriet the Spy”! The whole thing was obviously a colossal misunderstanding. My daughter was just a child… a soccer-playing, violin-practicing, Pokemon-card-trading child, not a proto-sociopath. Right?

Then I thought of a train journey I had taken many years earlier, from Dublin, Ireland, to Belfast, Northern Ireland, where I was living at the time. When the train stopped at Newry station for longer than the usual few minutes, I thought nothing of it, and when officials began to scurry over the platform, I tamped down my growing unease with an inner litany of “Nothing is wrong.” But when the conductor stuck his head in our car and yelped, “All of you, off the train!” I remember thinking, clearly and calmly, “if I leave my bag on the seat, nothing will happen.”

Minutes later, I was on the platform, watching flames shoot from the windows of my recently abandoned car. Like anyone else, it seems, I have a profound capacity for denial.

I don’t think I would miss a swastika. I don’t think I would miss the bombs being assembled in the garage or the trips to the gun show or the kind of rage that fueled those two boys in Colorado. But I can’t say for sure. To some extent our children will always be our babies, after all, and when we look at them we will see not the things they have hidden in plain sight, but their newness and helplessness. I suspect that my daughter will always be able to fool me into thinking she is faultless, for the simple reason that I adore her. At this point I may still have some control over what she reads and what she learns from it, but soon I will have very little. Then, I know, I will be in the same terrifying boat as every other parent: suffused with denial, desperately optimistic, blinkered by love.