The Stain. Stories of the Sixxth Dimension, #1

Dave is a guy who just wants to be left alone. He works an 8-to-5 at the warehouse, keeps his lawn trim, and tries to be a good husband to Sarah. But lately, the silence in his suburban cul-de-sac feels heavy. It starts with the new neighbor, a quiet man who moved in next door and never wave back. Then the small things start disappearing: a garden trowel, a bag of mulch, Dave's spare house key. Dave is sure he's just losing his mind-blaming it on the heat and the overtime-until he sees the neighbor watching his house from a darkened upstairs window at 3:00 AM.
Dave stops sleeping. He starts "monitoring" the fence line. He tells himself he's just protecting his home, but the obsession begins to rot his life from the inside out. He stops going to work to stay home and watch the neighbor's driveway. He starts hearing whispers in the vents and finds "marks" on his siding that look like code. When Sarah begs him to see a doctor, Dave realizes she's been compromised.
He's the only one who sees the truth. To save his family, Dave decides he has to strike first. He doesn't realize he's become the very monster he's hunting until he's standing in the neighbor's kitchen with a claw hammer, staring at a man who doesn't even know his name to be told.