Margo used to explain away all her mistakes with superstitions she had failed to heed or rituals she had failed to properly execute—the floors of Clark’s house had always been gritty with salt—and the woman could say something like, “Dreams are just our souls going for a swim at night,” with all the calm, bored confidence of a woman describing the laundry.

It had been Margo who’d instilled in Clark a lifelong aversion to the Flats outside the family’s house. Other children grew up with Bigfoot in the woods and the bogeyman under the bed, but not Clark. She’d been told stories since she was in diapers about a monster that slept in a trench under the Flats, coiled and lethal as a snake in a toilet’s U-bend. “The thing out there’s got long whiskers like a catfish,” Margo used to tell her daughter. “And nails as long as the school bus and two black iguana eyes that’re as big as your face.”

Looking back, Clark always thought that the monster had been a brilliant tool for a mother with a useless husband and two wild children to corral. The creature drank little girls’ tears, for one thing (“So quit your bawling unless you want him to come say hello”) and kept Clark well on her mother’s side of the property line. “Don’t you dare go over that fence, Starsha Marilynn Clark. Ain’t nobody goes out there in the Flats don’t get lost on the way back. And that’s how he gets you.”

The monster even had a name, though it was something so bizarre and alien it had always struck Clark as far too peculiar for her mother—a woman who was rather prosaic, under all the crazy—to have invented herself. Clark struggled now to remember that name, feeling suddenly as if it were a vital thing to know, though why on earth she suddenly cared after twenty years was beyond her. The name had sounded like something she’d find in the Old Testament, she remembered that much. “Botox,” Troy had called it once. “Bullshit.”

Margo hadn’t cared for that. “You just wait till you feel it moving in your sleep,” she’d told him. “Just you wait till he makes your nightmares go woolly—then you’ll know he’s took a shine to you.”

When Clark had discovered, much to her surprise, that none of the other children in her kindergarten had ever heard of a monster that slept under the Flats, her mother’s stories had quickly lost their power. But now that Clark, with more than a little fear, was approaching what she was certain would be a sixth night of troubled sleep, she couldn’t help but wish her mother were here with her tattered tarot deck and her prayer beads. Because Margo had been right about one thing: one afternoon, when her mother picked Clark up from the middle school, she’d greeted her by saying, “Next Tuesday’s the day.”

And sure enough, late on the morning of the following Tuesday—April 6, 2004—a pickup truck from Denton, Texas, had come roaring down the highway with Margo’s name all but written in blood on the front fender.