Conditionally reinstated in the Guild of Mages, scholar Edwin Blackthorn and his protector Julian Thorne are prisoners in plain sight. Forced to serve their hidden enemy, Magister Rowan, they are tasked with stopping the radical Erebus Society from finding the legendary Nocturne Key.

But the hunt reveals a shocking truth: the key is not an object, but a legacy flowing through Edwin's own veins. He is the only one who can open the final lock. Suddenly, Julian must protect the man he loves by leading him directly into a trap.

As they breach the final vault, they find their enemies waiting. The ambush is a perfectly laid deception, and they were the final piece. Betrayed and outmaneuvered, their only hope lies in one last secret their ancestor left behind—a truth that could either be their salvation or their ruin.