Manipulated by a time-traveling 1950's G-Man, an unwitting LAPD Detective risks her life tracking down three dangerous aliens who escaped from a secret military base through a time portal, to present-day Los Angeles, where they plan to destroy the world.
3 aliens, able to occupy different human bodies, are on a mission to kill all humans and wait for their fleet's arrival to Earth. A special agent and an LAPD detective are on their tail.