So there are couple reviews on this game, and one gave away the secret spoiler...highlight area below
Publisher Ubisoft has been extremely cagey about the game's long-rumored sci-fi trappings, but because they're revealed so quickly, it's not really a spoiler to say what we're about to say (although if you really don't want to spoil the game's first five minutes, go ahead and skip to the next page): Assassin's Creed actually follows two storylines. First, there's white-robed Altair, an arrogant young Assassin cultist who lives in the Kingdom of Jerusalem circa 1191, during the Third Crusade. Soon after the game begins, Altair botches a vital mission deep underneath Solomon's Temple; disgraced, he's given a chance to restore his honor by assassinating nine key Muslim and Crusader political figures, thereby restoring some peace to the region.
Then there's Desmond Miles, Altair's near-future descendant, who's kidnapped by a shadowy corporation and strapped into a machine that can unlock the ancestral memories stored in his DNA. His segments - which bookend each chapter of Altair's story - play a little like a point-and-click adventure and are confined to the lab where he's imprisoned. Why this layer of sci-fi weirdness even exists isn't clear at first, but it never feels tacked on, and the things you'll learn here will gradually cast an unsettling new light on Altair's story.