The story takes place a few years after the end of Splinter Cell: Double Agent. Don't worry, if you never finished that game, you'll get caught up quickly as to what's going on. Sam's daughter was killed, he murdered his best friend Lambert, and he split from Third Echelon, the government agency he'd called home for years. With new evidence leading to his daughter's killer, a tormented and semi-retired Sam Fisher is called back into action. Turns out the people responsible for his daughter's fate are planning a major terrorist attack on Washington D.C. This is going to be one long day for Jack Bauer Sam Fisher.
Conviction sets itself apart from its predecessors with its pacing. You're always being pushed forward, so much so that I played through the entire single-player campaign in one sitting without even realizing I'd been up all night. Ubisoft pulled off a few magic tricks to make this happen.
There are no in-game loading screens unless you die. From the moment the game starts, you never sit around waiting for something to happen. Levels are loaded while you're watching slickly presented cutscenes. Fancy new projection technology integrates text into the scenery to point you towards your goal, and back story is shown with movies playing out on walls as you progress through a level. These things aid in keeping players immersed in the world, but the real reason things feel so fluid is the change in approach to stealth.
In Conviction, stealth is about speed.