User blog comment:IIPKII/Whereabouts/@comment-179280-20130822230845

I think that Reiner, Bertholdt and Annie were sent to infiltrate the walls in search of the person who stole their "Titan Power" (Ymir) and a person who knows about the secret of the walls (Christa), but once they found out that Eren also had the Titan-Shifting ability, they switched their objective to kidnap him instead of Ymir. Of course, they later found out that she was a Titan Shifter too, so they kidnapped both of them and took them away. I still have to think of what are they gonna do to them, but I don't think it's because of what Ymir said (that they will kill her), because she was obviously lying so she could take Christa with her.