Sydney Bristow, an agent who has been tricked to believe she is working for the U.S. government, is actually working for a criminal organization named the Alliance of Twelve. Upon learning this, Sydney becomes a double agent for the real CIA.

FBI Special Agent Olivia Dunham, brilliant but formerly institutionalized scientist Walter Bishop and his scheming, reluctant son Peter uncover a deadly mystery involving a series of unbelievable events and realize they may be a part of a larger, more disturbing pattern that blurs the line between science fiction and technology.

Stripped of everything, the survivors of a horrific plane crash must work together to stay alive. But the island holds many secrets.