When Michelle receives a call from a Richmond historian, she sees the chance for a much-needed adventure. All she has to do is find a century-old key. Three others - a guitarist, an engineer, and a retiree - receive similar calls. Each family possesses a key to a four-lock safe found buried in a Virginia courthouse, though their connection is as mysterious as the safe itself. Their ancestors should not have interacted, had no apparent reason to bury the safe, and should not have disappeared thereafter. Bearing their keys, Michelle and the other descendants converge in the courthouse basement and open the safe, revealing the truth about their ancestors - a truth stranger, more deadly, and potentially more world-changing than any of them could have imagined. Now it's up to them to keep their discovery out of the wrong hands.