A shocking discovery is made on the episode "The Man from the Other Side." That's not unusual for Fringe, of course.
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Olivia and Peter take cover in this scene from Fringe. It's courtesy of the episode "The Man from the Other Side."
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Olivia takes cover and takes aim in this photo. It's courtesy of the episode "The Man from the Other Side."
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Fringe Season 2 Episode 18 Quotes

I'm not from here am I? You just didn't open up a hole from the other side. You went through and you brought me back. That's why I was able to survive Newton's device.

Peter

I am not your son.

Peter