Deus Ex: Human Revolution gives players a story that's already fully realized, but the upcoming "Missing LInks" DLC will flesh out a section of Adam Jensen's adventure that the original game glossed over. There is a segment in the original game where Jensen is forced to turn himself into cargo, and while the original release seemed to imply that the voyage was uneventful, in reality he was found, his augmentations were reset to zero, and Jensen was forced to fight his way to freedom.
This new section of the game takes place on a ship at sea, and it's hard to avoid getting a Metal Gear Solid 2 vibe from the proceedings. Jensen sneaks around, takes out fools when necessary, and the rolling sea provides a suitably epic backdrop. While very little was added to the story in the preview code I was able to play, we're being promised that new layers to the conspiracy will be uncovered during this portion of the game, and new characters will be introduced.