The film is set in 2018 in a post-apocalyptic world where the human race is at war with Skynet and its army of deadly Terminators. John Connor (Christian Bale) is a young soldier who is destined to become the leader of the human resistance.

However, he is forced to question his certainty about the future when a mysterious stranger named Marcus Wright (Sam Worthington) suddenly appears, and John must decide whether he has been sent from the past or the future. As Skynet grows more and more powerful and all hope for the human race looks like being eliminated in one final devastating attack, John and Marcus journey to the centre of Skynet's operations where they discover a shocking secret...