Fate Stay Night 19th Episode.

The battle continues between Saber and Assassin, Shirou and Kuzuki, Rin and Caster. Saber defeats Assassin just before dawn but Shirou can't match with Kuzuki and he has his sword destroyed and then he falls in the pit with Rin. Caster is about to blow them away when Saber arrives and attacks her altought she can't use her Noble Panthom anymore. Caster gives a speech saying she'll spare Shirou's life if Saber will become her Servant as Assassin before. When he hears this words another Servant that was hidden appears and tells that Saber in a property of his own and he kills Caster throwing on her dozens of blades. Since Caster is dead the entire cave is collapsing, so Shirou takes Sakura who's still unconscious and escapes with Rin and Saber. After that Rin, Shirou and Saber discuss about the new Servant at Shirou's house, Saber says that she fought with him in the final fight of the Holy Grail Battle, that he's obtained the Holy Grail and that his wish was to remain at this world. Then Rin goes to watch over Sakura who hasn't wake up yet. Saber and Shirou goes outside, Saber confess Shirou that she wants to come back in the past to choose a better king, that her former Master was his father who was in her opinion the perfect magician but he betrayed her asking her to destroy the Holy Grail, thus now the only way to have a wish granted is to create a new Holy Grail as Caster was trying to do. Shirou is astonished so he goes to talk with the priest that arbitrates the Holy Grail Battle. He confesses that if a Servant drinks from the Holy Grail won't be a Servant anymore, but when Shirou mentions the eighth Servant he's astonished too.