In the year 2077, Tech 49 Jack Harper (Tom Cruise) is one of the last drone repairmen stationed on Earth.
According to Jack, the planet was nearly destroyed sixty years earlier,
during a war with a race of alien invaders known as Scavengers
("Scavs"). The Scavs destroyed the moon, causing massive earthquakes and tsunamis, and then launched their invasion. They were only defeated by the use of nuclear weapons, which left most of the planet irradiated and unlivable. The few surviving humans migrated to a colony on Titan, which is powered using energy harvested on Earth by giant ocean-borne power stations that generate fusion power from seawater. From Tower 49, a base standing above the remains of the northeastern United States, Jack and his partner and lover Victoria "Vic" Olsen (Andrea Riseborough)
work as a team to maintain the autonomous drones that defend the power
stations from the few remaining Scav bandits. They receive their orders
from Sally (Melissa Leo), their mission commander, who is stationed on the "Tet," a massive tetrahedral
space station that orbits the Earth. Jack flies recon and repair
missions to the surface, while Vic supervises from Tower 49. The two
expect to leave Earth and join the other survivors on Titan in two
weeks. Although Jack and Vic had their memories wiped five years prior
for security purposes, Jack has recurring dreams about meeting a
mysterious woman at the Empire State Building
in a time before the war, which occurred before he was born.
Additionally, Jack keeps a secret retreat in a forested area on the
surface he sometimes visits.