How much would you sacrifice in the name of loyalty? Otis Oppenheimer never once pondered this question. He should have. Young and eager to prove himself, Otis felt the pull of something extraordinary when, in 1986, he and a select group of agents were handpicked by Ronald Reagan for a clandestine mission known as the Glass Onion initiative. The task seemed straightforward: scour the globe for a mythical glass onion, rumored to grant its...