Peter's less concerned with the plausibility than with the danger. He doesn't think giving Olivia a massive dose can possibly be safe and Walter admits that the side effects could mean stopping Olivia's heart, phasing in and out, disappearing altogether and/or bursting into flames. Fortunately, he has the official Fringe waiver ready for her to sign. Most of it's just boilerplate, Olivia, don't sweat it.
Peter's adamant that Olivia not do it, but Olivia asks what choice they have, because they have to rescue Michael. "Etta died so that we could finish the plan," she points out. Peter asks what happens if Olivia dies. Well, then humanity is screwed, which is kinda where you are now, Peter, so this better not just be about having someone to have sex with until humanity as we know it ends. Of course, the other thing I'm not clear on is how this Norwegian scientist essentially invents the Observers when he's already living in a world of Observers, like some kind of Terminator closed-loop paradox, but I promise not to worry about this more than four or five more times through the rest of the recap. "Without him, we lose everything," she says.
After a few moments, Peter calmly starts pointing out problems with the plan, assuming she even makes it over successfully: They have no idea what or who is over there anymore, since they closed the bridge 24 years ago. For all they know, the Observers invaded over there too. "We have no way of knowing what happened," he says.
It's Astrid who points out the cracked universe window in the corner and suggests looking through it to the other side. "That's brilliant, Ashcan!" crows Walter. Peter remains skeptical.
Back over the neurological research unit of Liberty Island, an Observer scientist injects poor Michael to paralyze him for the neck down so he can't interfere in their diagnostic testing, which involves lowering a huge contraption down over his head and studying the results on a screen. Windmark stares at him. Dude, more blood from your other nostril! Michael is staring at him, looking almost challenging. If I had to guess, I'd say he's thinking, "I can keep this up all day, old man."
The Fringe team pulls their van up in Battery Park by the water. Liberty Island is in the distance and there is a so-brief-why-bother concern over a Loyalist woman walking her dog by the water, but then she just decides abruptly to turn around and walk the other way, so they're all clear. With Olivia and Peter on lookout, Astrid and Walter start hauling the gear out of the van and setting up the window. They flick it on and look through it hopefully, and behind the glass, images of people passing by flicker into view as does the full Statue of Liberty in the distance in her rightful place (not counting the mini ones in Las Vegas or Paris). "Isn't she beautiful," says Walter. Olivia seems a little less reassured than he does, but she's the one making the journey.