Ayman al-Zawahiri, a 59-year-old Egyptian-born doctor, is expected to become the leader of al Qaeda now that Osama bin Laden has died.
The Wall Street Journal describes al-Zawahiri as even more radical than bin Laden, though it notes he lacks the latter's wealth and charisma.
A trove of computer data discovered at bin Laden's compound, detailed here by Politico, could help the U.S. intelligence community learn more about al Qaeda and potentially even track down al-Zawahiri. Until then, he remains on the FBI's Most Wanted List and a major threat.
The CIA has had close calls in capturing al-Zawahiri before. Still at large, al-Zawahiri released a video on the Egyptian uprising earlier this year, stating democracy "can only be non-religious." He once called President Barack Obama a racial epithet.