I've often criticized this show for its lack of focus when it comes to its own mythology and with this episode, it seems like the overall arc of the series has finally lurched foreword. This in itself is a good thing as it gives Fringe a sense of direction, but I felt that this episode was appealing for another reason -- it gratifies me to see people doing things simply because they are the right thing to do.
This brings us to Dr. Boone who not only gives his wife his own spinal fluid, but later sacrifices himself to save her and then delivers on a promise as one of his final acts. Does this really excuse him doing work for ZFT? That's debatable, but a story of sacrifice and plain-old goodness in the face of evil is usually enough to make me happy.
Fringe has been hit or miss for me; Mostly miss, but if they take the lessons of this episode and focus on humanity instead of sensationalism, I think this could become a worthy successor to The X-Files.
"Midnight" could have been another boring monster of the week episode, but it redeemed itself with Dr. Boone and his quest to simply do the right thing.