Late last night he had a headache and high fever, and right when I was about to take him to the infirmary, Skeith took over (without the normal hair and eye change). He said that he "failed," and passed out.

I left the room to find help and saw Mon (the ghost, I'm pretty sure you've met him) and Fuuka. Mon and I talked to Fuuka a bit about her sensing a "third presence" in Haseo and how that could relate to what just happened, then headed back to his room to take him to the infirmary... He wasn't there, and when Fuuka tried to sense him, she said it felt both like he was on the island and that he wasn't there.

We suspect this has something to do with those blue butterflies, because one bit him a while ago.

See my reply to Jean's comment.