Two kids smoke up in a parked car outside a warehouse listening to Rush. One of the windows of the building near them explodes and the stoned dude decides to go check it out.
It's abandoned and empty inside, with shattered windows and a growing lump of something on the floor. Like any normal dude, he picks up a stick and pokes at it. Then an alien-looking shape shifter comes up behind him and snaps his neck. He puts a device in the dead kid's mouth and puts the other end of the cord into his, slowly morphing into the kid.
Back outside, not-Dave gets in the car with the girl and promptly kills her as another shape shifter comes around the corner.
Peter (Joshua Jackson
) comes over to find his dad obsessing. He tries to distract Walter (John Noble
) with plans to bake a pie, but Walter tells him earnestly there's something Peter deserves to know. He begins a speech about every living thing dying but is interrupted by Olivia (Anna Torv
The Fringies go check out the girl, dead in the car. The case was flagged when someone found the telltale three puncture wounds in the soft palate, caused by shape shifters, Olivia knows. Newton (Sebastian Roché
), their leader who kidnapped Walter a few episodes back, must be up to something.
They find the girl's joint. She has lipstick on, but it's lipstick-free. She was with someone. Into the creepy warehouse they go. They find dead Dave (James Pizzinato
), with holes in the roof of his mouth.
Then they see the ball of goo that was growing and now looks sort of like a giant brain covered in a thick membrane. It's the size of an ottoman.
Walter cuts it open, it oozes mercury. He pulls out a not-at-all-organic-looking block.
The two teens, now dressed as shape shifters, meet Newton. They tell him the third didn't make it.
Back at the lab, Walter dissects the shape-blob. He's figured out it's an undeveloped shifter.
Broyles sends them a file of a TV broadcast signal near the warehouse. Walter thinks the interfering signal might have come from the other side. They turn it up and slow it down. Astrid (Jasika Nicole
) thinks it sounds like a language.
Olivia takes it to Massive Dynamic, where the head nerd tells her it's radio waves, trig equations. He tells them the astronomy division picked up a solar flare around the same time. He agrees it could have come from a parallel universe, where things would be slightly out of sync. Sometimes, however, they perfectly line up. His computer is telling him that's going to happen tomorrow at 3:31 p.m.
Newton hands out assignments. One of them will be a man named Wu (James Tsai
) and another will be McAlistair (Peter Bryant
). They'll meet at 3:20.
The girl suggests aborting because they're a man down, but Newton says they won't have another chance for seven months. They're going through with it.
Chestnutt Hill, Mass.
The girl shifter approaches McAlistair, asking for directions.
In the lab, Astrid tells Peter that Walter is trying to remember what he told Newton so they can be prepared. Peter looks at his dad's things and finds an old family photo.
He checks with Olivia. He tells her he thinks he knows why Walter's been so weird. He thinks Walter wants to talk to him about how his mother died. He knows it wasn't a car crash-- she committed suicide.
He got the news from Walter when he was in the institution, the only time they spoke in 17 years.
Olivia reminds Peter his dad loves him.
Walter comes in with a plan to find out what they're up to. He'll need six car batteries, a voltage transformer, electrical wire -- and a corpse, one which hasn't been dead for more than two days.
Newton walks into a bank and asks to see the manager, McAlistair. They're not sure what to do about Verona (Shawn Macdonald
They go into the safety deposit room and Newton consults a device to measure a spot on the floor, then burns a hole through it and put a rod in place.
At the lab, Walter hooks the shape shifter embryo up to the electricity and the corpse, which he hopes to question. They give it a little juice and the embryo glows. More juice, the power blows. The embryo pulses and glows and starts to move, trying to break out of its skin. It breaks through like the grossest baby bird you've ever seen, except person shaped. But it seems to die. Walter thinks he hurt it during dissection.
They're about to hook it up when it suddenly comes to life, grabbing Walter. It begins to talk with difficulty. It tells them to contact Newton through Daniel Verona. Olivia asks what's going to happen tomorrow. It takes Walter's hand, says it's sorry and dies.
FBI agents swarm a man coming out of a store. It's Daniel Verona.
Newton calls in to 911 that a middle-aged man is having a heart attack, then he steps out and takes a pill. Then he appears to have a heart attack.
At FBI HQ they test Verona, but don't think he's a shifter. He's a medical examiner at Boston General.
At the hospital, someone wheels a covered corpse into the morgue and leaves. The corpse climbs out of the bag. It's Newton, alive. He consults his device and marks another spot, placing another rod.
At the Bishops, Walter is a bundle of nerves, blaming himself for the shape shifter dying. Peter tries to calm him down and calls him "Dad."
Walter suddenly realizes he thinks he knows what Newton is up to.
He explains he and William Bell sent his car to the other side using geometry and harmonic vibrations, with three harmonic rods in a triangle. Then they activated the rods. The car vibrated and went to the other side.
He thinks if the rods are sent up at the exact same place on both sides, whatever's in the middle will be exchanged when the universes are in sync.
They have 10 hours to figure out where the center of Newton's triangle is.
The shape shifter in the form of Wu sets up another device in a telephone pole's utility box.
Back at the lab, the Fringies assume Verona had access to one of the points. Astrid reports on McAlister's body being found with three punctures to the soft palate.
They circle the two points, the hospital and McAlistair's bank. Because they're looking for an equilateral triangle there are only two possible points: Hyde Park or in the middle of the Charles River, on a condemned railway bridge. Olivia assumes it's the bridge because the water will absorb the excess energy.
At the bridge, the sifters gather. A cop car pulls up on the bridge.
The Fringies race there, with teams looking at the other points for the harmonic devices.Walter's trying to calculate a way to cancel Newton's device using opposite harmonic vibrations.
They arrive at the bridge and are greeted by two police officers. One tells Olivia he needs to call his sergeant and she pulls out her gun and shoots him in the head (the cell phone was the giveaway). As Olivia and Peter are stuck in a gun fight with the remaining shifter-officer, Walter sees it's 3:30 p.m. and drives onto the bridge.
Nearby, Newton activates his device. The water under the bridge pulses and vibrates.
Peter races to join Walter as Olivia keeps shooting. He helps his dad unload his device.
Newton tells his shifter to aim for the Bishops.
Walter starts his program but the laptop isn't calculating properly. Peter says he can fix it and sends his dad off with Olivia.
The bridge vibrates and shakes violently and another bridge appears. Peter sees a man walking toward him. There's an ear-splitting whine and an FBI agent next to him disintegrates in a flash.
The man keeps walking toward Peter from the other side but he gets his program to work and the other side bridge disappears with a pulse throwing Peter back into his car.
When he wakes up, he's in a hospital and Olivia is there. He's been unconscious for 36 hours.
Peter tells Olivia he wants to talk to his dad alone. Peter addresses his dad seriously, telling him about the man he saw walking toward him and the way the other agent died. The vibrations didn't kill the man from the other side, he says, and they didn't kill him.
"I'm not from here, am I?" Peter asks. "You didn't just open up a hole to the other side, you went through and you brought me back."
Peter realizes it's why he survived and why he can't remember his childhood and why his mom killed herself, from guilt. He's pissed, and won't let Walter call him "son."
He asks to be alone.
Newton addresses a man he calls "Mr Secretary" (whom we can't see) and tells him that despite preparations, crossing over is an ordeal. He gives the Secretary some sort of sedative.
Back at home, Walter is finishing up making a pie and frantic to go visit Peter. Olivia comes over. She tells him Peter's gone.