My thing is this:
The girl is really his daughter, or her he promised her real father to look out for her (he knows she used to have highlights, so he has been watching her for a while)
And I think he is dying, he is going to go out with a bang.
I think she's his daughter, but I don't think he's dying. I think someone found out who she really is and that person(s) are out to injure him through her. I also suspect that she may be his biological daughter, but not the one he abandoned as described in the first episode.
After all, who really is watching her? The FBI? Spader? Who is it?