Demon frames a local legend: Mariah Peggot, the least celebrated of four Peggot sisters, falls for Romeo Blevins, an older, handsome mobile mechanic. Despite Mrs. Peggot’s warnings, Mariah sneaks around, becomes pregnant, and moves into Romeo’s A-frame outside Duffield, believing she’s won a prize.

Romeo soon cheats and turns violent. In one assault, he ties Mariah to the deck, shoves a gun in her mouth, and draws a mocking smile and heart on her skin, leaving her to watch baby Matty cry inside. Later in winter, he repeats the tying; Matty weakens in the cold and hunger. Desperate, Mariah prays and decides that “mad is better than sorry.”

Mariah tapes an X-Acto blade to her body. When Romeo passes out after another binge, she flips him and carves a permanent smile into both cheeks and a heart on his chest, then flees with Matty. She assumes he will accept blame and not press charges.

Instead, Romeo hires an expensive lawyer who paints Mariah as a jealous, unstable stalker and disputes paternity. With era norms and a doctor’s testimony about Matty’s dehydration, the jury believes Romeo’s story. Just eighteen, Mariah is tried as an adult and sentenced to twelve years, sent to Marion.

In the aftermath, townspeople eventually shift sympathy toward Mariah and dote on Matty, whom Mrs. Peggot raises while bearing gossip about turning her daughter out. Romeo disappears. Demon admits the tale haunts his nightmares and feeds his own fantasies of carving a smile on Stoner, revealing how cruelty breeds the urge to strike back.