An award-winning Iranian nuclear scientist traveled to Saudi Arabia earlier this year to perform a religious pilgrimage. He never returned.

Shahram Amiri's mysterious disappearance is turning into a Middle Eastern whodunit involving nuclear secrets and political intrigue, with a new round of accusations emerging this week and the U.S. government still refusing to comment.

There are two big questions: Was Amiri spirited away by Saudi-backed American covert agents? Or did the scientist seize the chance to defect to the West, offering sensitive information in exchange for asylum?