In Philadelphis, the Police Officer Daniel Gillespe receives a phone call and leaves his partner alone to pick up a briefcase in a Train Station. When he catches the object, his body hardens and blows up killing eleven people. Soon the Fringe Division investigates and discovers that it was not a terrorist attack with a bomb; instead it was Gillespe's body parts that killed the passengers. Dr. Bishop finds in the autopsy that something was injected in Officer Gillespe since there are needle marks in his toes. However the footage from the surveillance camera does not help since there is static blurring the image. Peter and Olivia head to Gillespe's house to interview his wife and Olivia accidentally finds a hidden compartment with the drugs used by Gillespe. Soon they discover that an AWOL colonel, Raymond Gordon, may be behind the explosion. Meanwhile Peter and his father seek out a new apartment to live and Olivia meets Sam Weiss to treat her physical and mental problems.
Peter, Walter, Olivia and Broyles pursue a strange and deadly occurrence in Philadelphia where a bomb blew up inside a train station but left no trace of any explosive device. The perplexing and unexplained set of circumstances returns Walter to the lab to closely examine the human remains where he uncovers an unlikely energy source that triggered the explosion. With the explosive threat of more bombs and links to a classified military project, the intense investigation leads Olivia and Peter to Iraq.
The Fringe division investigates the explosion of a police officer. Olivia starts having visions about her experience on the other side.
Two cops stop for coffee. One remains in the car and takes a call from someone he calls "Colonel," who tells him to go to the train station and look for someone in a black trench coat with a black briefcase. The cop drives off without his partner. At the station the officer finds someone who fits the description and confronts him. He pulls his gun and demands the man's briefcase. He grabs it. Nearby video terminals fuzz out. His hand freezes. It travels up his arm until he crystallizes into a thousand tiny bits and explodes.
Olivia (Anna Torv) prepares for some bowling and brain work with Sam Weiss. He helps her tie her shoes. He guesses she hasn't been sleeping and has lingering pain from the accident. He's surprised her headaches haven't started yet. He tells her to come back tomorrow.
Peter (Joshua Jackson) reads classified ads for apartments to his dad. Walter's being picky. Astrid (Jasika Nicole) finds a report about the bomb in Philadelphia. They can't find any trace of explosives.
At the station, the agent in charge tells Olivia about the lack of forensic evidence. The surveillance cameras only show magnetic static. Walter (John Noble) finds a red crystal he guesses is shrapnel from the bomb. He licks it. It's salty.
Peter finds another odd piece of shrapnel - Officer Gillispie's badge. But there were no officers taken to the hospital. Walter brings over his red crystal. He thinks it's organic. Upon closer inspection it's a rock solid red ear. Walter just found Officer Gillespie (Phillip Mitchell).
Back at the lab Walter examines Officer Gillispie, trying to figure out what made him explode.
Peter's computer guy shows them his cleaned up version of the surveillance footage. It's still grainy and cuts out before the explosion. He says high radio frequencies can cause picture to fuzz out.
In the lab, Walter reminisces about a jigsaw puzzle he and Peter put together when Peter was 10 -- 500 pieces of a Playboy centerfold. It reminds him of the task at hand. Walter has laid out all the crystallized pieces of Officer Gillespie on a table. It's a bunch of rocky, glass chunks with a foot and partial hand. He found needle marks between the toes. He was probably injected with some sort of transformative serum solidifying the water in his cells and emitted massive energy which shattered him. Walter stopped counting at 47 needle marks. Gillespie did it to himself. They figure Officer Gillespie was the bomb.
Peter and Olivia meet with his widow. She says he did two tours in Iraq. As she's talking, Olivia starts feeling exceptionally odd. She grabs her head and runs for the bathroom. She sees flashes of the alternate world she visited and throws up. While down on her hands and knees in the bathroom she notices a tile not quite in place in the wall. She removes it and finds a small kit filled with vials and another box with a syringe.
Olivia is puzzled because Gillespie doesn't fit the profile of a bomber. They take the vials back to Walter.
Oak Park, Illinois A woman gets out of bed in the middle of the night. She takes the same kind of kit Gillespie had out and prepares an injection, which she shoots between her toes. It's clear she's been doing it frequently. It briefly crystallizes her foot as it flows in.
The next day, the woman loads groceries into her car. A man walks up to her. It's the Colonel. He calls her Captain Burgess and tells her he's moving her to active status and she needs to go to D.C. He gives her a cell phone like the one Gillespie had. He asks if she's been taking the serum and tells her from this point on "Tin Man parameters are in effect."
Olivia visits Sam Weiss and asks about her headaches. He essentially tells her her brain is waking up and she's getting her memory back. He gives her bowling shoes and tells her she's going to keep score by hand for a kids bowling league. For starters, it might teach her some patience.
At the lab, Walter says based on the amount of serum in his body, Gillespie would have had to inject himself daily for at least a year -- which would have started when he was in Iraq. He thinks there's a trigger to activate the serum. Peter asks if it could be a radio wave, like the one causing the surveillance fuzz out.
Astrid pulls up Gillespie's record and finds mention of a chemical weapon his whole unit was exposed to. They should all be dead. It's called Project Tin Man and it's classified.
Peter and Olivia meet with Broyles (Lance Reddick), who says Tin Man was shut down. The names of the military personnel in the project were redacted, but three Iraqi doctors are listed. Peter thinks he knows someone who can help, but he needs to go to Iraq. He'll need private air transportation, $20,000 and a passport without his real name. He's still on a few watch lists, so Olivia will go with him. Broyles doesn't want to send her, but he wants to keep the trip quiet.
Iraq Peter and Olivia walk into a darkened hookah lounge. Peter walks up to Ahmed (Patrick Sabongui), a man with a badly scarred face and greets him in Arabic. Peter tells him what he's looking for. The man heard Peter had been killed, but tells him he knew it couldn't be true because Peter is too good at looking out for himself. He's not inclined to help. But Peter tells him he's trying to save lives. Peter gives him the doctors' names. The man tells them to have some tea while he goes to see what he can do.
In the lab, Walter injects some of the serum into a watermelon. He's still trying to determine what triggered the bomb. He fiddles with radios. The lights in the lab flash and the watermelon starts to shake. Walter is giddy over his experiment but suddenly it stops. There's a pause. Then the melon explodes.
Peter and Olivia get a stiff drink. The man comes back for them and brings them to one of the doctors. Dr. Yusef (Navid Negahban) is now a dishwasher, considered a traitor by his people. Olivia mentions the name Tin Man and the doctor gets very nervous. But he tells them about it. He says they developed a daily treatment to counteract the chemical weapon. Only four people in the program survived. One of them was Diane Burgess.
The doctor says an unintentional byproduct of the serum was turning people into bombs. He tells them about a Colonel who wanted to continue the program. His name was Raymond Gordon. The doctor warns them Gordon is a vicious man.
Broyles briefs agents on Diane Burgess and the fact they believe she's in D.C. and is a bomb. They've picked up the other two people from the program. Back from Iraq, Olivia tells the agents about Gordon, who went rogue a few months ago. They're hoping to jam the detonation signal. Olivia mentions they don't think Burgess knows she's a bomb. They get a report Burgess is in a cab. They rush there and set up first, hoping to stop her and catch Gordon. On surveillance they see her answer the cell phone Gordon gave her.
In the surveillance van, Peter and Walter figure they can trace Gordon's radio signal but only if they don't jam it. They decide to follow Burgess in the hopes they'll find him. They think they have about 30 seconds from when he activates the signal until she detonates. Inside, Gordon calls her and tells her to look for someone in a black trenchcoat with a briefcase. Peter sees her inside. The radio signal hasn't been activated yet.
She sees the person with the briefcase and approaches him. He doesn't know what she's talking about. Gordon activates his signal and Walter starts counting from 30. In the surveillance van, they find Gordon's signal is too powerful for their jamming equipment. Time ticks down.
Peter and Olivia look for Gordon frantically. Burgess' hand starts to crystallize. Peter sees Gordon and tackles him. A transmitter flies out of his pocket. Olivia tries to turn it off as Burgess turns to crystal. Finally, Olivia bashes it to bits with her cane and saves the day. Burgess slumps to the ground, but in one piece.
Back at the lab Walter brings Peter a classified ad for an apartment.
At the bowling alley Sam Weiss measures Olivia's hand and tells her to go home. She gets frustrated. As he's talking about finding her the perfect bowling ball she comes up behind him and pulls her gun on him, telling him to quit wasting her time. He pauses and looks to where she was sitting. Her cane rests on the chair. She's standing without it. He says he'll see her tomorrow.
Gordon tells Broyles the end is coming and they had to take matters into their own hands. He says "they" are here, collecting data, making observations. That's what's in the briefcase. "They" have been passing information to a courier. As he says this we see the trenchcoat man Burgess tried to intercept bringing his briefcase to someone who loads their food up with pepper. Gordon says whatever's in the briefcase is going to destroy us all. We see it's The Observer (Michael Cerveris) who received the packet. He thumbs through the photos inside. They're of Walter.