It has an improved multiplayer, a new squad command ability as well as a Zombie Mode.
The mission starts with you exiting a Pave-Low at a Spec Ops base in Britain. You meet your new squad and learn the buttons etc. then get on a Pave-low and fly off.
Your objective is to free captured civilians and retake the train station. You silently eliminate enemy forces then breach and clear the reception. A train arrives full of enemy soldiers all of whom you kill. Your team sniper comments on how well equipped they were. The end cutscene shows that they were supplied by Op-For.
You take control of Sergeant Nixon.