Morrowind's story, like any good story, begins with a stranger shrouded in mystery...
...and ends with a cataclysmic battle. Unlike most, where the hero is a renegade hated by all but those whom he intends to save, you are universally reviled by everyone but your masters... and to them you are ultimately a tool to be used. You must gather your strength, prove your mettle to one and all, unite a peoples that has been fragmented over and over for milennia, and defeat an inimitable remnant from a bygone era. (Herding cats may seem easier in comparison)
If you come to the realisation that you have screwed up the Main Quest beyond all salvation, there is an alternative route. It's not nearly as fun, but it's here just incase.