Attack on Titan: Season 1, Episode 17

1 - 17: Female Titan - The 57th Exterior Scouting Mission (1)

As the Scout Regiment begins its push toward Shiganshina, they encounter an intelligent Female Titan unlike any they've seen before. When Armin hypothesizes that it's really a human that's been turned into a Titan, he, Jean, and Reiner attempt to stop it.