A convoy of police cars, lights flashing, tail the large yellow truck up to the back gates of London’s British Museum. It’s just before 3 a.m. on July 10, a date that has been kept under wraps for months. After the truck pulls into the museum’s loading bay, four men open its back doors to reveal a cage-like rectangular crate. Inside it is another crate, inside that crate is a metal shell, and inside that shell, folded back and forth on itself 28 times, is a precious and fragile artifact, nearly a thousand years old. The journey this truck has...