Warning! Text may content spoilers about the game storyline, its predecessors or the books on which the game is based on
Unfortunately, for the this moment we know only some general ideas about Witcher's 3 storyline. We know the base of the story, but the details, like the main characters or quests for Geralt, are still unknown.
So what will be the problems Geralt will face? As we remember, Witcher 2 ended up in a one big mess in the Northern Kingdoms, due to the actions of killers of the kings, sorceress's schemes, Nilfgaardian Empire and little fights between remaining monarchs. But this time, politics won't be the biggest concern for Geralt.
In the third part, our hero is old and tired, that's why he returns to his core - he mounts a horse and rides into the world to travel and kill monsters, and try not to get involved in anything else. But it's not a senseless travel. Before the end of the Witcher 2 Geralt regained the memory fully and get to know that he isn't the only one who was thought to be dead due to the Rivia's Massacre five years ago (described in the last book of series by Andrzej Sapkowski). What is more, he knows also that his love, Yennefer, is "looking after" by the emperor of Nilfgaard, Emhyr var Emreis.
That's why Geralt should, first of all, get to the south, to the capitol of the Empire and find the sorceress (but this search shouldn't cover the whole game). The quest isn't simple, because when you begin to play, Nilfgaard gathers its troops at Yaruga river to attack the Northern Kingdoms once again.
How will that affect White Wolf's actions, we don't know yet. But he will travel not only the banks of Yaruga, but also Redania on north (with its capitol, Novigrad) and Skellige Islands on west from the main continent. Will Geralt seek help to get south in those places? Or maybe finding Yennefer isn't his only priority?
For confirmation of those information we have to wait. We don't know also if the mysterious white-haired person, who accompany Geralt on one of the screens, is Ciri , "surprise child", and the most important (even more than Yennefer) person in the Geralt's life. If that'd be true, the scenario will get one of the most important plots joining the games with the books. What is more, the same main plot in the Witcher 3 may be things left unsolved in the books of Sapkowski and finally dealing with the Wild Hunt. The latter one is a group of ghost riders, travelling the skies - who are, in fact, the reflections of elves from the other dimensions, who try to hunt down Ciri, Geralt and Yennefer, to get the girl.
At the end, it's worth mentioning the old friends who may appear in the game. For sure, we'll meet Dandelion, dwarf Zoltan Chivay and a sorceress Triss Merigold (whose situation is interesting due to the seeking of Yennefer by Geralt). There is also a high probability that other witchers from Kaer Morhen will show up (or at least the old Vesemir, who appeared even in the first cinematic trailer). The remaining characters - like Vernon Roche, Iorweth, Letho, Shani or Alvin - are unknown for the time being.
For persons who haven't played in previous games or read the books of Sapkowski, this text will be very mysterious or even not comprehensible. But don't worry, to enjoy Witcher 3 you don't have to know the previous games and books. Fans of this universe will be able to grasp more references and correlations, but the remaining players will have a journal with the lexicon. What is more, producers announced that explanations or reminders of the past may be done even when you stop playing for a longer time.
That'd be all about our current knowledge concerning the storyline of Witcher 3. If CD Projekt RED tells something more, we'll add information onto our website.