What is the most shocking takeaway from the story of the two 12-year-olds who repeatedly stabbed their friend — nearly to death — on the imagined orders of a fantasy character?

Is it the preteens’ apparent disconnect from the truth of what they were doing? One of the assailants childishly described her actions to police in their comfy Milwaukee suburb as “stabby, stab, stab.”

Is it the girls’ seeming belief in the reality of a cartoonish character known as Slenderman, a faceless being in a tie, jacket and hat? The girls reportedly found him on a harmless-fun-sounding website called Creepypasta Wiki.

Slenderman resembles the Invisible Man, played with evil lunacy by Claude Rains in a 1933 movie. “Slendy,” as his “followers” call him, exists in an online subculture in which fans elaborate on a legend. (His creator, Eric Knudsen, says he’s “deeply saddened” that his character inspired this terrible crime.)

Or is the most alarming part of the story that parents in Waukesha had never even heard of Slenderman, much less that this fictional presence had become an obsession of their sixth-graders?

The most jarring item in this list has to be this last one.

Heartless crimes fueled by delusion are not new. In the ’70s, the infamous “Son of Sam” shot and killed six people in New York, he said, on the orders of a neighbor’s dog.

From what we know so far in the Wisconsin case, the girls, charged as adults with attempted murder after stabbing their friend 19 times, haven’t shown they understand the seriousness of their actions.

One told police in a fairy tale cadence: “The bad part of me wanted her to die. The good part of me wanted her to live.”

And as already noted, there isn’t anything especially realistic about Slenderman. He’s not so terrifying as the vampire Dracula, who sent the “three sisters” to prey on his victims. And he’s less plausible than Bigfoot, the hairy humanoid said to lurk in the woods surrounding every Scout campfire.

What makes this case very modern is that the parents seemed unable to act as intermediaries between their children and their children’s darkest fantasies. And how could they when the imaginings were hidden in their kids’ online lives?

The fairy tale goblins of yore were passed on through books the parents read — or at least put on their shelves. When the Creature From the Black Lagoon appeared on the television screen the family shared, the parents could say, “He’s not real.”

In a paper-based past, evidence of an unhealthy fixation, written or drawn, would be found strewn around a child’s bedroom. There would be comic books. Young people might reveal their preoccupation in semi-public phone calls, not messages quickly tapped out and silently sent by electronic means.

I offer no answers here. It’s hard to expect parents — busy in their working lives and their own online adventures — to monitor the every interaction of children approaching adolescence. And how many could find these deep cyber-recesses if they wanted to?

Furthermore, how many would have seen danger in a fascination with such a silly character as Slenderman? (Some might have seen value in the creative activities he seemed to spawn.)

As I said, no easy answers here. These days, we are communicating in less physically public ways. Banning teens from participating in the online culture would seem impractical, unfair and a handicap to their development.

Perhaps this is just a repeat of those rare but awful crimes involving children in the past, with a 21st-century update. Perhaps. But these girls should be studied carefully.

Froma Harrop is a syndicated columnist. Follow her on Twitter @FromaHarrop. She can be reached at: fharrop@gmail.com.