Despite the incident's gravity and its lingering influence on Islamist terrorism, the Grand Mosque's siege is a historical footnote nearly 40 years later. Saudi Arabia quickly shut down its communication channels to the outside world as the event unfolded. Since then, it has had no desire to discuss the most destabilizing and embarrassing moment in its history, when militants seized and held Islam's holiest shrine for 15 days, and Riyadh had to rely on clandestine members of the French special forces to regain control. But as the recent plot and the kingdom's enduring fight against radicalism underscore, the legacy of the 1979 Grand Mosque siege lives on....