4:54am. The snowy dead of winter. Gunnar Floss walks into a rural New England 24-hour diner. He approaches the local police chief, bleary-eyed after a long overnight shift. "I done it," Gunnar says. "I killed Mary." It has to be joke. The diner boys put him up to it. Gunnar's been harmless all sixty-two years of his life - just collects deposit bottles and eats salvage food alone in that old house his crazy father left behind. And his only connection to the supposed victim is the backwoods grade school they both attended fifty years ago, when she was the daughter of town royalty and he was the unwashed outcast that everyone pitied, if they noticed him at all. The joke is over when Mary McCaslin is found brutally murdered in Gunnar's barn. To learn what could linger in this solitary man's mind for half a century and bring him to murder, police Chief Elton Moran must face the shame of his own childhood as a bully. And when this insular New England town closes ranks around Gunnar, Chief Moran finds himself on the outside. Gunnar Floss Killed Mary McCaslin is filled with the complex characters and atmosphere of a Ruth Rendell or Louise Penney novel: the greasy diner, the pine hills, and the rundown barn where Mary McCaslin now lies dead.