Hiding out in Goa, India with girlfriend Marie (Franka Potente), Bourne (Matt Damon) is set up in a crime in Berlin. The group that set him up looks to kill him as well but only succeeds in pulling him out from hiding by killing Marie.
Meanwhile, Pamela Landy (Joan Allen), deputy director of the CIA is investigating the death of politician Neski, who died 7 years previously in suspicious circumstances. As Bourne is alleged to have killed her own leads into the real cause of Neski's death, Landy is forced to hunt for Bourne herself, while uncovering secrets that go deeper into the American secret service that anyone previously thought.
The Bourne Supremacy has a far darker story than that of the original (Identity). The shock killing of Marie at the beginning is testament to this and shows that the book's writer (Robert Ludlum) was about to have some soppy love story ruining a perfectly good spy/action film.
The film benefits greatly from this. Not because Potente is a poor actress but more because with the addition of Joan Allen she may well have been overshadowed by another strong piece of acting. Her character, Landy, plays a role very similar to that of Bourne in the first film as she slowly starts to discover more about the organisation that she works for.
Supremacy adds more action to a series that already contains a huge amount. One of the (two) car-chase sequences is phenomenal and one can only imagine the costs that director Paul Greengrass put the funding through to make his vision a reality. Simply. Stunning.
The film also gives itself to the trilogy far more than the first film. Where Identity has a perfectly acceptable ending on its own, Supremacy uses scenes from the third film (Ultimatum) to mean that once it is finished you are begging for further answers.
Assuming you have the third film ready and raring to go, you need to start watching this. Now.
Seriously, stop reading.