20. Erwin Smith - The 57th Exterior Scouting Mission (4)

Complete story — includes the ending

Though the Female Titan is restrained, the squad is unable to extract the human inside as she is able to crystallize her skin to prevent them from cutting her skin. Everyone realizes it was Erwin's plan to use Eren as bait to draw out the mole within the army who joined them after the Walls fell; that's why he kept the plan from all current members and only revealed it to those who were part of the Scout Regiment before the fall. The Female Titan suddenly hollers a scream that draws all Titans in the vicinity towards her. Despite the Scout's attempt to stop them, the Titans ignore them and eat the Female Titan's body in a frenzy. Thus, Erwin calls off the expedition. With no confirmation that the mole inside has also been eaten, Erwin orders Levi to replenish his gas and gear just in case before returning to his squad. The mole is indeed alive; disguised as a cloaked Scout Regiment member, they attack Levi's squad and kill Günther.