The Witcher 2 Assassins of Kings

Story

The plot of The Witcher 2 is intended to be less linear than that of the first game, and is supposed to feature "three independent plot lines" which lead to multiple endings.
The Witcher 2 is set almost immediately after the first, and follows from the attempt on King Foltest's life which occurred in the final cutscene. Geralt will once again face the mysterious witcher-like assassins, who appear to be connected with a character named in previews as the Kingslayer. In a trailer, the Kingslayer is seen speaking to Iorveth, a human-hating elf. The Kingslayer displays a head which he claims belonged to King Demawend of Aedirn, and says that if Iorveth is prepared to help, more kings will also fall.
Other plot elements which have been referenced (but which do not necessarily correspond to the three plot lines mentioned) are Foltest's moves to capture the stronghold of the rebellious Baroness La Valette and "Geralt’s personal theme, in which he’s looking for his own identity".
According to a fact sheet released for the game, Geralt's travels "will lead him up the river Pontar into the turbulent borderland between Temeria, Kaedwen and Aedirn". A town named Flotsam, situated on the border between Temeria and Aedirn, will feature.

Characters returning from the first game include Triss Merigold, Zoltan, and Dandelion. A new character to be introduced is Vernon Roche, a member of the Temerian military who has been sent to help Geralt. Though it is not not known where in the narrative it will take place (if at all) it may be speculated that Geralt will face off against a dragon. (may be speculated from the original, leaked, gameplay trailer from September '09 which shows a dragon along with another of the mysterious assassins). Also a concept piece shows what looks like some form of dragon in the background of it, the only living thing in view. (to the right hand side)

 Demonstrated segment

A small segment of the game's early stages has been covered in some detail by previews and videos, apparently having been used as a demonstration for the media. In the final game, some or all of it may vary depending on player choice.
The segment begins with Geralt, Triss, and Roche on a ship, presumably on the Pontar river. They disembark and head into a forest, with Triss and Roche arguing. They are interrupted by the sound of someone playing a flute, and notice Iorveth watching them. Roche and Iorveth know each other, at least by reputation, and are hostile. A fight begins, with Iorveth signalling archers to attack — Triss is able to establish a shield to protect them (seen in the trailer), but is weakened by the effort, and needs to be carried by Roche. The shield renders Iorveth's archers useless, but enemies can still pass through the shield on foot, and Geralt must hold them off alone while the three slowly make their way to safety.
At some point after this, the three are admitted to the town of Flotsam, where they find a public hanging in progress. Two of the four people waiting on the gallows are Dandelion and Zoltan, the latter of whom turns out to be an informant that Roche was looking for. Geralt moves to save them, arguing with the guards (with some support from the townspeople) and then fighting them. The town's leader then arrives and speaks with Geralt — the two unnamed prisoners are hanged, but Dandelion and Zoltan are spared, with the town official telling Geralt to speak with him later to hear a proposal.
Geralt can later visit a nearby elven ruin which the rescued Dandelion informs him of. This involves fighting their way through a stretch of forest, and then fighting looters at the ruins. Triss accompanies him, and when they find themselves trapped after a fall, there is an opportunity for a love scene (possibly the one depicted in the trailer, as it supposedly takes place in a ruined bathhouse).
At some point later still, Geralt accepts the town official's quest and must fight a large monster that Geralt knows as a tentadrake, which may also be depicted in the trailer.