S1E16 : Nunnally Held Hostage

C.C. departs as a messenger to the Chinese Federation and Milly has a marriage interview with Lloyd Asplund, creator of the Lancelot. Mao returns to kidnap Lelouch's sister, Nunnally, and holds her hostage in the Ashford Academy sewers. Lelouch and Suzaku work together to rescue her, with Suzaku's physical adeptness and the clever use of Lelouch's Geass proving to be beyond Mao's planning. Before he can be arrested, Mao reveals that Suzaku killed his own father, and in return Lelouch silences him with his power. C.C. returns to the campus and finally ends Mao's life as Suzaku crumbles to the ground, confronted with his actions after years of secrecy.