Jennifer Garner stars in this mystifying series as Sydney Bristow, a grad student who's also a double agent for the CIA and one of its adversaries, SD-6. Bristow transforms herself -- literally and figuratively -- from a rookie into a veteran agent. As she stays constantly on the run from unknown enemies, her penchant for disguise helps her while she contorts through every plot twist and confounding situation. Michael Vartan co-stars.