Some doors are hidden for a reason. Others are sealed to protect the world from what lies behind them. When Avi uncovers a mysterious structure long dismissed as myth, he believes it to be nothing more than a forgotten relic. But the door was never abandoned-it was designed to wait. Across generations, the Noor family has guarded fragments of a truth too dangerous to be written down: the knowledge to rebuild a lock that cannot be forced, only understood. As ancient engineering collides with modern ambition, Avi is pulled into a race against time that stretches across continents and centuries. Each discovery tightens the grip of a mechanism built with a singular purpose. Because the first door is not the only one. And opening it may be the last choice anyone ever gets to make.