Fifteen years ago, 8-year-old Ethan Jones watched a stranger bury something in the mining ruins of the Rhyolite Desert, Nevada.

Even at his young age, he knew what he’d just seen was important.

In present day, a US Navy SEAL takes refuge in a secret chamber beneath the ancient streets of Syria and discovers an unusual stone artifact, like nothing he’d ever seen before.

When news of the discovery reaches Sam Reilly, he is forced to return to his past, where his search for the Master Builders originated – and complete a mission he’d hoped could have stayed unfinished forever.