Young teenager Sam Witwicky becomes involved in the ancient struggle between two extraterrestrial factions of transforming robots – the heroic Autobots and the evil Decepticons. Sam holds the clue to unimaginable power and the Decepticons will stop at nothing to retrieve it.

Thirty years ago, aliens arrive on Earth. Not to conquer or give aid, but to find refuge from their dying planet. Separated from humans in a South African area called District 9, the aliens are managed by Multi-National United, which is unconcerned with the aliens' welfare but will do anything to master their advanced technology. When a company field agent contracts a mysterious virus that begins to alter his DNA, there is only one place he can hide: District 9.

Sam Witwicky leaves the Autobots behind for a normal life. But when his mind is filled with cryptic symbols, the Decepticons target him and he is dragged back into the Transformers' war.