Nunnaly is missing, of course. In her place, Lelouch has a brother, Rolo. He's obviously a spy of some sort.
He is the pilot of the experimental Knightmare. And he has a geass of his own.
Meanwhile, the Emperor shows Suzaku his secret: the Sword of Akasha: a weapon to kill God.
Roll comes to the embassy as Zero is broadcasting. But right then, he gets a call from Lelouch! How?
In fact Lelouch is back at school.
The Office of Secret Intelligence can't detect Lelouch behaving any differently, not even with 180 hidden cameras and 47 undercover observers.