The story begins with Mark Brewster, a man recently released from a mental institution after being declared cured of violent tendencies. Mark returns to his ancestral home — a brooding, isolated estate with a massive stone wall running behind it. He hopes to start over with his young wife, Elena, who supported his treatment.

But peace is fleeting. From the moment he returns, Mark becomes obsessed with the old garden wall behind the house — a crumbling, moss-covered structure that seems to “move” when no one is watching.