Let's follow up now on what appears to be a serious blow to the regime in Syria today. A blast repeatedly killed the country's defense chief, the brother-in-law of President Bashar al-Assad and wounded other top officials. This explosion, we're told, occurred inside the tightly guarded national security headquarters in Damascus. To sort out what we know, or don't know, about this incident so far, we've called Neil MacFarquar. He's a correspondent for the New York Times. He's in Beirut. Welcome back to the program.