When a Russian spy defects to the United States with reports of an assassination plot against the US President, the CIA send in Agent Evelyn Salt to take his statement. None of his claims seem to have much worth until he names her as the Assassin. Fearing the agency will act on the Russian's claims, Salt takes flight, on a solo mission to clear her name. But as her efforts to find the real conspiritors bring her dangerously close to the President and further claims from the Russian defector that she is a part of a long rumoured sleeper-spy program, the Agency find it harder to believe her cries of innocence and have everybody asking "Who Is Salt?"