The film begins in 2013. Deep beneath the Pacific Ocean, a fissure opens up, that leads to another dimension.
Through the fissure, a colossal monster identified as Kaiju appears, and destroys portions of San Francisco.
A war erupts that results in countless casualties and quickly consumes humanity's resources.
After many days and a growing death toll, the creature is defeated by human military forces.
However, what seemed to be an isolated attack builds, as more creatures begin to come through the fissure, attacking coastal cities around the Pacific.
The World unites to stop the invaders, and build The Jaeger Program: a series of giant mechanical 'monsters,' intended to stop the creatures.
These massive mechs, known as Jaegers, which are controlled simultaneously by two or three pilots whose minds are locked in a neural bridge.
Original tests to have one pilot per Jaeger prove unsuccessful, as the test subjects were not able to handle the stress and strain of controlling such a huge robot by themselves.
It was then decided that each Jaeger would be piloted by two pilots, their memories linked together in The Drift, synchronizing their movements to maneuver the massive machines.
As the Jaegers go to work, they begin to turn the tides, and take down the creatures (known as Kaiju).
Pretty soon, the world is enthralled by the Jaegers and their pilots.
They become celebrities, and even have merchandise made.
As well, the dead Kaiju are soon seen as a black-market commodity, their parts sold off for various collections and medicinal purposes.
But just as the war seems to be turning in humanity's favor, the Kaiju's attacks become more frequent and more brutal.
In 2020, seven years after the fissure opened, one of the more famous Jaeger duos is Raleigh Beckett, and his older brother, Yancy.
Pilots of the Jaeger named "Gipsy Danger," they have become heroes with an impeccable record of defeating Kaijus.
Raleigh and Yancy are instructed to suit up to fight a Kaiju heading towards Anchorage, labeled Knifehead, a designated category III in danger and size.
They wade out into the Pacific in their Jaeger with orders to kill the Kaiju and save the city.
The beast is larger and more powerful than previous category three's and will be a challenge for the team.
Though the information on their monitors shows a small fishing boat in the path of the attack, the Becketts are told to ignore the boat, their priority is to protect Anchorage.
Raleigh ignores the command, and attempts to save the ship. He and Yancy believe they are victorious after shooting Knifehead with the plasma cannon built into the right arm, and prepare to leave.
Knifehead reappears and attacks as the Jaeger is turned, ripping off Gipsy Danger's left arm, and causing Raleigh permanent damage.
Knifehead then attacks the head, ripping it open and killing Yancy.
Raleigh is devastated by his brother's death, and barely manages to pilot Gipsy Danger on his own.
Raleigh kills Knifehead, but receives severe damage to Gipsy Danger in the process.
Exhausted and emotionally distressed, he limps the Jaeger ashore to a remote beach on the Alaskan coast, much to the amazement of a father and son who witness the event.
Raliegh emerges from the broken hull of Gipsy Danger dazed and bloodied before falling to the ground unconscious while the father sends his son off to get medical help.