He doesn't remember much, having been knocked unconscious. He just remembers trying to get Mikasa so they could escape, and then Reiner showed up, and then...nothing.

When he woke up, he was no longer at the medical facility but instead in the woods. Lost, alone, and with none of his friends in sight. What the hell happened?

Now, he wanders through the woods alone, trying to find Mikasa and the others. Hopefully, he won't run into one of those hollows...