At Massive Dynamic in the monitor room, Walter is using a bong and telling a security guard that he was sleeping with Yoko Ono. When the guard points out that being CEO of Massive Dynamic is impressive, Walter admits that he hasn't accomplished much. He contemplates the rhythm of people moving through the hallways on the monitors, and notices one room that no one enters. The guard explains that it's Walter's office.
Two hours later, Walter brings a cart filled with boxes from Bell's office to Nina Sharp. Nina wonders why he's going through Bell's old files, and Walter insists that he's trying to find a way to stop the worlds from colliding. He explains that Peter is happy for the first time because he and Olivia are together, and now he knows what his failure will cost. Walter explains that he and Bell worked together, and he went through Bell's files to find a way to try and think the way that he used to, when anything was possible.
At the Massachusetts Metal Depository, two men seemingly ascend the outside wall. When they get to the top, they flip over and don boots that are waiting for them, and are able to stand on the street: they've actually climbed down in a reversal of gravity. A security guard spots the second man, and is forced to shoot him when the criminal goes for his gun. The guard then stares in shock as the dead man and his blood drifts upward.
At the Harvard Engineering Building, Peter tests the memory disks that he recovered from the shapeshifters. He links them together and starts tapping the information, but has no idea how to read it. Olivia calls to invite him to a street fair, and Peter lies and says that he's at the gym. He says that he'll meet her at the house in fifteen minutes and hangs up, and Olivia gets a text message from Broyles summoning her to the Depository. She gets there with the Bishops as the police pull down the dead man. Broyles explains that the upper windows don't have alarms, and the two thieves used their "ability" to get to the windows. Walter checks the man and wonders if he is a man, while Olivia gets a description of the man who escaped. An agent finds a key card, and the patrolman confirms there are no scanners in the building. Peter finds the weighted boots that the thief used as a counterweight. Walter examines the body and discovers that the leg muscles have atrophied as if the thief spent a great deal of time in outer space, but there's sign of similar expected atrophy in the upper part of the body. Olivia gets word that the depository is missing a substantial quality of osmium. Walter notes that it is twice as dense as lead, the heaviest element on Earth.
At Frost Aerodynamics, Dr. Krick is leaving via the parking garage when he sees the thief, Bill. Bill tells him that the other thief was shot, and he's feeling nauseous unlike the last time. Krick tells the thief to go to the lab and wait for him, and then leaves. Bill gets into his car, using weighted boots as counterweights.
At the Harvard lab, Walter has Peter look through Bell's files for references to floaters and anti-gravity. He examines the body and confirms that there are no traces of helium or lighter gasses. He does discover that the man has a low white-cell count, meaning whatever is making him float, and continue floating after death, is attacking the body's defenses. Peter notes that the anti-gravity effect is wearing off. Olivia arrives and reports that they haven't found the other thief based on the witness description, but the key card belongs to a warehouse in Allston. As she leaves with Peter, Walter smiles and notes that when he and Elizabeth were courting, they'd take walks to parks rather than warehouse.
Krick goes to the warehouse and uses his key card to enter the area he owns. Bill is there and asks what is happening to him. His eyes are bleeding, and he notes that Krick said that once they got more of the osmium, the effects would be permanent. Krick warns that he can't defy gravity without consequences, and mixes a liquid. Thanks to Bill's sacrifice, he'll be able to eliminate the side effects. When he turns around, he discovers that Bill is dead.
At Harvard, the corpse suddenly falls to the ground. Walter times the effect and notes that it is inconsistent. He tries to help Astrid lift the body, and realizes that it is too heavy. He tells Astrid to take another blood sample and test for osmium.
As they drive to the warehouse, Peter and Olivia talk about the things they dislike about the other in the interests of full disclosure. Olivia insists that it's a matter of trust.
At the warehouse, Krick is dissecting Bill's corpse when he sees the landlord let Olivia and Peter in. They find Bill's corpse and confirm that it matches the description of the second thief. Spotting an open door, they go inside and find a room filled with corpses.
Walter is summoned to the scene and confirms that they all died of osmium poisoning, and the osmium was given via injection. The bodies were cut up after death as a form of autopsy. Walter admits that he has no idea how injections of the world's heaviest element would make someone float. Broyles reveals that the local police have found eight wheelchairs, and confirms that the eight dead men all suffered from long-term muscular dystrophy. Walter realizes that the atrophy signified long-term confinement to a wheelchair, and Peter notes that no one in a wheelchair would turn down the chance to fly.
Krick goes to the gym where handicapped men are playing wheelchair basketball, including his son Michael. As Krick sits down, he notices one handicapped teenager, Vince, watching from the stands. The doctor asks why he isn't out there, and the teen admits that he's not healthy enough to play. Krick offers to give him a miracle.
At the Harvard lab, Walter is examining solidified osmium taken from the dead men's blood. Meanwhile, Peter and Olivia try to find a connection between the eight men. He suggests that they take a break and go out for pizza. As they go, they find Nina in the hallway. She says she's there with a file for Peter from Massive Dynamic, and Peter realizes that Walter told her that they're together. Peter says the file is background on shapeshifters. As Olivia takes a call, Nina tells Peter that he's made a wise decision to go forward, and he and Olivia deserve to be happy.
In the lab, Walter insists that the person responsible is altering the fundamental forces of the universe, defying physics. He demonstrates by putting a mint into a bottle of soda, setting off a geyser. Nina comes in and asks what the problem is, and Walter admits that he needs Bell because he's failing to solve the case. He gets out a file on soul magnets, research that Bell did on the principle that a person's consciousness lives on after death. All that is required is to put the microscopic magnets into the host body, and Walter wants to do it to bring Bell back. Nina assures him that it was Walter's imagination that was his most valuable asset, and that he won't fail because he can't.
Krick gives Vince an injection of the modified osmium, and the boy rises out of his wheelchair and then drifts toward the ceiling. The doctor gets him back into his wheelchair and gives him a pair of counterweighted boots to hold him down. However, Krick admits that he doesn't have what he needs to make another batch, and Vince offers to help him get it.
At the lab, Walter uses liquid nitrogen to melt the osmium. He explains to Astrid that since the person responsible has reversed the laws of physics, they've allowed the osmium to melt when exposed to cold instead of heat. There is a white substance mixed in with the melted osmium, and Walter tells Astrid to call Olivia back.
Krick helps Michael into bed and then leaves, saying he has some late work to do at the office. Michael tells him not to push himself too hard, and Krick says that he's close to a breakthrough that will change everything. Michael assures him that he's never failed, just as he never has in the past. Comforted, Krick wishes his son good night and says he'll see him in the morning.
Walter examines the second element as lutetium, also incredibly dense and rare. He realizes that lutetium could be found in meteorites on display at the Museum of Science's astronomy wing.
Vince uses his anti-gravity abilities to break into the museum via the skylight. Outside, Peter and Olivia meet with Broyles and find the counterweight boots.
Vince lets Krick into the museum after disabling the alarms. Krick gets his samples, but Olivia and the others arrive. The doctor abandons Vince, who releases his tether and starts to drift toward the open skylight. Olivia shoots at the door ahead of Krick, forcing him to stop. Meanwhile, Peter runs up to the catwalk next to the skylight and leaps onto Vince, dragging him down to the ground before he can drift into the sky.
Peter and Walter bring Michael to see his father in jail. Krick admits that he hurt some people in wheelchairs while trying to help them, and did it for his son. Michael insists that he was happy and didn't need fixing, and wheels away without another word. Peter goes after him, and Walter relates the story of Icarus and how the wings he gave his son killed Daedalus. He notes that other parents weren't as fortunate as Krick's, and asks how he defied the laws of physics. Krick explains that he works in aeronautics and was contracted to build an ultraweight alloy. He combined the two dense elements and created a molecule lighter of air. Krick admits that it should never have worked, but it did and it was a miracle.
Later, Walter comes to see Nina and explains that Krick merely took advantage of the changing laws of physics, and those laws are breaking down because of what Walter did 25 years ago. When Nina notes that he's taking it well, Walter says that he's figured out how to stop it and hands her one of Bell's files.
Peter invites Olivia to the engineering building and explains that he hasn't been entirely honest with her. He explains that he can't trust what he's been doing with Walter or the FBI, but wants to show her.
Walter takes the antique bell that Bell left to Nina. He figures that the emanations from the bell will bring forth Bell's consciousness and rings it. He stares at Nina, who says that it's still her, and explains that wherever Bell is, he'll find them.
Peter shows Olivia his private office, which contains every bit of knowledge they know about the Machine. He shows her the shapeshifter disks and she realizes that he got them by killing the shapeshifters. As Olivia examines them, she hears a faint ringing in her head. As Peter explains that he can't decrypt the information, Olivia turns and says that the decoder key is in "her" office: Bell's office at Massive Dynamic. She turns and, speaking in Bell's verbal cadences, says that it's good to see Peter again.