i don’t remember that story. But I admit I read the book a long time ago.
It was in the movie. A couple in a distant future are agonizing over whether or not to kill their children in their sleep because of the impending doom coming the next day. They don’t do it.
But the next morning, when the mother wakes, and realizes it didn’t happen, With great joy she rushes to her kids’ room, only to find her husband kneeling over the bodies of their children that he killed in the night.
With what is coming, I suspect there will be at least some “non-Christian” parents killing their own children out of misguided “compassion”.