Ep 17. Mark of the Witch

In Fate/stay night season 1 episode 17, titled "Mark of the Witch," we see Shirou and Saber continue to investigate the recent murders in the city, which seem to be connected to the Holy Grail War. They quickly discover that the latest victim had a magic crest on her body, indicating that she was a mage.

Meanwhile, Rin and Archer are carrying out their own investigation, but come to a dead end when they are attacked by a mysterious woman named Caster. Caster reveals that she is the one responsible for the murders, and is targeting mages in order to drain them of their magical energy to strengthen her servant.

As Shirou and Saber confront Caster, they are joined by Archer, who has managed to break free from her control. However, Caster proves to be a formidable opponent, using her magic to control the surrounding environment and prevent the trio from escaping.

As the battle intensifies, Shirou realizes that Caster's true identity is that of the legendary witch, Medea, and her servant is the great hero, Heracles. Shirou quickly formulates a strategy to defeat them, which involves using his own limited magical abilities to create a diversion while Saber and Archer go in for the kill.

In the end, the plan works, and Caster and Heracles are defeated. However, Shirou and Saber realize that there are still many more powerful opponents waiting for them in the Holy Grail War, and they will have to be even more prepared if they hope to come out victorious.

Overall, this episode is a thrilling and action-packed installment in the Fate/stay night series, with plenty of twists and turns to keep viewers on the edge of their seats. The battle scenes are beautifully animated and the character development is top-notch, making it a must-watch for any fans of the series.