Season 1: Walt is Abducted/ Hatch is Blown Open
Season 2: Penny finds the Island/ Others capture Jack, Kate, Sawyer
Season 3: The Flashbacks are now Flashforwards & they have to go back
Season 4: Locke is the mysterious Jeremy Bentham & he is dead
Season 5: Juliet detonates the Hydrogen Bomb
Season 6: The survivors “move on.” They were all dead.