William Bell shows Walter his very own universe of hybrid creatures on a hologram. He's excited to finish making it. He says couldn't stop it now if he wanted to. Bell is chalking Walter's arrival up to divine intervention. He's excited to share the moment with his "dearest friend."

Peter and Olivia return to the empty lab. He asks her about the "Jedi mind trick" she pulled on the roof with David Robert Jones. She's uncomfortable, but chalks it up to cortexiphan. She agrees to let Walter run tests when he returns.

Olivia gets a call from Jessica (Rebecca Mader), who Olivia cured of nanites with her kinetic powers. Jessica is worried someone is following her. We see someone standing in her kitchen. Olivia says they'll be right over. The person in Jessica's kitchen is September, our favorite Observer (Michael Cerveris). He starts to follow her through the house, but he walks over a symbol on the floor that glues him in place.

Olivia and Peter reach Jessica's house. The door is open, her purse and phone are on the table. There's a big hole cut out of the floor where the Observer was trapped.

Broyles calls, Astrid was just brought to the hospital with a gunshot wound following an anonymous 911 call. Astrid is out of surgery.

At the hospital, Astrid tells them they went looking for William Bell in the waterfront warehouse. She wasn't found there. She feels awful she couldn't protect Walter. She tells them where to find the warehouse and that it was full of strange animals.

Olivia and Peter go to A1 Imports warehouse. She wonders about the connection between the nanites and his using the sun's power to collapse an oil reserve.

The warehouse is empty except for the Observer, glued to his piece of cut out floor. He tells them he's not there of his own volition.

Jessica walks out with a gun on them. If they ever want to see Walter alive, Olivia has to drop her gun. The Observer is immobilized and can't help. She works for Bell, she was infected intentionally.

The Observer is concerned about the events in Olivia's life and Bell said if they put Olivia's life in harm's way, he'd appear.

She fires at the Observer three times. He catches each bullet. They operate in hyperattenuated time -- they can move very fast.

She takes out a gun Bell invented that shoots faster. She shoots. The bullet hits the Observer. Olivia gets angry, asking Jessica what she wants.

Jessica shoots at the Observer again, but Olivia stops the bullets with her powers and flings them back at Jessica, killing her.

September is surprised they knew how to trap him. Peter scrapes the glowing symbol off the floor and frees him. The Observer doesn't know where Walter is. Now they know how the Observer gets shot. Olivia asks him about what he told her at the Opera house, that in every version of the future she has to die.

September says it hasn't happened yet for him so he goes to investigate the future and find out what he meant.

They take Jessica's body back to the lab to interrogate her dead body. Nina Sharp shows up to help, not caring for now how Peter knew they had the technology.

Olivia is angry about being manipulated to activate her powers. Nina figures William Bell needs something only she can provide.

At sea on Bell's version of Noah's Ark, Walter asks Bell why he's doing this.

Bell tells him this was all Walter's idea. He was angry with God after Peter died twice. He wanted to create his own universe that would operate by his rules. But when he realized he could actually do it, he got scared and had Bell take that part of his brain out -- to put the genie back in the bottle.

Bell got cancer and started dosing himself with cortexiphan to slow it. He says it's their destiny to act as gods since they're able.

Walter objects. "Dear friend, even if you deny it now, you've always been playing God. I am," Bell says.

Back in the lab, they jolt Jessica and she starts talking. Her eyes go googly and they try to get her to focus what she's saying. She says he's on a boat. They ask how he's going to collapse the two universes. She says he needs an energy source. They can't get her to say what he's going to use.

Olivia grabs on to her and demands and answer, but she blows out all the electricity in the lab and essentially re-kills Jessica.

Olivia realizes she's the energy source.

They scan her, she's giving off a ton of electromagnetic energy. Nina thinks she can trace Bell if he's using that power.

The go to the FBI and find a tanker left Boston port 6 hours ago but it's not on the radar. Nina explains that Olivia's frequency will match the one where the universes are overlapping, so they search for it. He'll be hiding out there, in the eye of the storm.

Olivia goes to an empty room to contemplate what Bell has in store for her. Olivia feels the same way she did when Bell was doing experiments on her as a child. Peter reminds her this time she's not alone.

On the ship, Walter looks at an old gun in a case in Bell's office. Bell insists he look out the window. The sea is roiling and full of electrical charges and creepy storm clouds.

In the lab, they find Bell's frequency. Broyles calls for helicopters. Olivia, Peter, Nina and Broyles head out. On the ship, Walter begs Bell to stop. Bell says they deserve it.

They get to the spot and no one can see the ship except Peter, because it's on the other side. Olivia can jump between universes and Peter can see it. Nina assures her she has the power.

Peter and Olivia climb out of the chopper. "If you've lost your mind, now would be the time to tell me," she says to him. Peter gives directions to the chopper pilot and they jump.

They phase into the other world and land on a container.

Bell recites Yeats as Walter fiddles with the old gun. Bell doesn't stop him. Peter and Olivia bust in.

Bell welcomes them as his Adam and Eve. Peter aims at Bell and commands him to stop the collapse, but Bell explains that the chain reaction has begun and it can't be stopped. With every breath Olivia takes, they head toward the inevitable collapse.

Walter aims the old gun. He shoots Olivia in the forehead. She drops, the electrical storm stops, the ship appears on our side on a clear day.

Peter runs to her. "You killed her!" he says. "Yes, indeed he did," Bell says. He rings his soul Bell and laments to Walter how happy they could have been. He phases away.

Walter tries to get Peter's attention, saying they only have a few minutes. Peter is gripped with pain and crying and holding on to her. Walter slaps Peter to get him to focus and calls for a letter opener. They put Olivia on a table.

Cortexiphan is regenerative and her brain is soaked with it. He thinks if he can get the bullet out, she has a chance, just like his lemon cake.

He digs the letter opener into the base of her skull to create an exit wound. Using a snapped off antennae he drives it through Olivia's skull. He hopes that any damage he does will repair itself. He taps the antennae in her head and the bullet casing pops out the back of her head.

They both wait.

Slowly, the bullet hole closes. Olivia starts breathing.

In DC, Broyles learns that there are no traces of Bell anywhere. His animals are being cryogentically frozen for his team's future study. They're granting his funding request and he's promoted to general.

Nina greets him outside. He asks her to run the new fully funded science division. "Nina, you want a job?" he says.

In the hospital, Peter and Walter wait in the hall. Walter thinks after all this Olivia will have almost no cortexiphan in her system -- no more lighting fires with her mind.

A nurse walks by with a tray of urine samples. Walter asks if it's lemon jello. When told what it is, he says "well, in that case no thank you. I'm more pekish than thirsty."

He thinks Olivia will be normal now. Astrid joins them. The doctor tells them Olivia's ready to go home. Peter goes to see her.

Astrid presents Walter with a bouquet of Red Vines. He gets her name right.

Peter brings a newspaper in with a house for them. She thinks it's perfect.

"I suppose he was right, the Observer, in every version of the future you had to die. But I don't ever want to lose you again," he says.

He hugs her but he can tell that there's something else.

"Peter, I'm pregnant," she says.

It's a big happy family reunion as Walter and Astrid join at the doorway.

Harvard University

Walter goes poking through the fridge and makes himself a late night PB & J. September joins him.

"We have to warn the others -- they are coming," he says.

"Who's coming?" Walter asks.

Source: IMDB