WASHINGTON, D.C. ó Last summer, Jake Sullivan was traveling with his boss, Secretary of State Hillary Clinton, when he disappeared during a stop in Paris. He showed up a few days later, rejoining Clinton in Mongolia.

In between, Sullivan secretly jetted to Oman to meet with Iranian officials. The July 2012 meeting is one of the administrationís earliest known contacts with Iran and reveals that Sullivan was involved in that outreach earlier than has been reported.

The secret diplomacy may seem like a tough assignment even for a grizzled foreign policy veteran, but Sullivan is just 37. Heís now Vice President Joe Bidenís national security adviser. Sullivan remains loyal to Clinton and is seen as her likely pick for White House national security adviser, should she run for president again and win.