Those aforementioned human/machine hybrids are what Olivia and co. have been calling the Shape Shifters (a.k.a. Charlie) and they're on a mission to find their leader. Apparently, their leader's head was being kept on ice in a cryogenics lab in our universe. Olivia knew where, but she couldn't remember. She finally recalled the location, but received a sudden text from Charlie telling her that Nina (whom she was in the middle of conversing with) was the Shape Shifter. She excused herself and met Charlie outside. She, unfortunately, filled him in on the location before she got the text from Massive Dynamic that showed Charlie was the true Shape Shifter. After she killed Not-Charlie, she was racked with guilt. Even worse, the human/machine hybrids got the head and were in the process of re-attaching it to the body. Looks like there's about to be an inter-universe showdown.
Huh? Moment of the Hour: Walter's former test subject reactivated her ability to spot the Shape Shifters (they appear with a light around them) and suddenly discovered that Peter had that same light around him. Walter had mentioned earlier that her ability simply allows her to spot those who don't belong and we know that Peter is really Alternate Universe Peter. Could this be why he was giving off the outsider glow?
Fringe airs Thursday nights on Fox. If you missed this week's episode, you can watch it for free at Fox.com.