Remember...a great war is supposed to break out between the Republic and the True Sith Lords. So, in my opinion, it will start off in the middle of the War, the Exile has left in your care, the Ebon Hawk and its crew (T3, HK, and Bao-Dur) in the care of you, a mere Jedi Padawan who many have seen as one of the savors of the Republic. When the war starts to go down, you are sent to find Revan who can save the war. You must travel to multiple planets to find clues to where Revan might be. Which includes the appearance of the party members of both games.