Season 3, Episode 16
Air date March 11, 2011
Written by Josh Singer
Graham Roland
Directed by Brad Anderson
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Cast | Transcript

"Os" is the sixteenth episode of the third season of Fringe.


The Fringe team investigates a case of thieves stealing rare metals that appear to float from the ground. Walter identifies traces of the elements osmium and lutetium in their blood, the alloy inexplicably creating a material lighter than air. They discover the culprit, Dr. Krick, an aerospace engineer who discovered the alloy and saw to try to detoxify it as a means to allow his paraplegic son to walk again.


The Fringe team is called to the scene of a robbery of a metals repository; the body of Koenig, one of the thieves, shot by a security guard, inexplicably floats off the ground, while a second culprit has gotten away. They find that the thief has taken off with a supply of osmium, one of the heaviest elements, and an autopsy later reveals that the dead thief's body is filled with the metal. Tracking a security card on the body, they enter a warehouse where they find the second culprit Bill, dead, along with the bodies of several more people, all of them paraplegic. Walter Bishop identifies the physical behavior of osmium has been reversed, and by melting the osmium collected from the first victim using liquid nitrogen, they find the presence of the rarer element lutetium, typically only present in meteorites.

Recognizing that the local science museum has a display of meteorites, the Fringe team is able to secure Dr Krick, the man behind the osmium injections, and Vince who has taken Dr Krick's injections as they attempt to steal the display. With Dr Krick in custody, Walter learns that the man had worked in aerospace to find an alloy for fighter craft. He happened upon the combination of the osmium-lutetium alloy that generated a material lighter than air and sought to refine a permanent solution to give his own paraplegic son, Michael Krick, the ability to walk, having promised the same to those that had died from earlier, lethal doses of the alloy.

Walter, who has lamented to Nina Sharp his need to have William Bell back to make himself whole, realizes that the only reason the osmium-lutetium alloy became lighter than air was due to his own transgression into the parallel universe that has started to break down the laws of reality. To reverse those effects, Walter intends to use the idea of "soul magnets", microscopic devices that can be ingested by a person to call forth the soul of another. Walter believes Bell had arranged for someone in the prime universe to be his vessel and rings the bell that Bell had bequeathed to Nina, believing it the instrument that will activate the soul magnets and call forth Bell.

Simultaneously, Peter Bishop has decided to open up to Olivia Dunham and shows her the five data discs from the Shape-shifters he killed after the doomsday device weaponized him. As he discusses it with her, Olivia hears the sound of the bell. She turns to face Peter, revealing herself to now be possessed by William Bell.

Notable Quotes[]

Olivia: So Walter, whereabouts in Boston would he be able to acquire lutetium?
Walter: It's mainly found in meteorites. Do you think the perpetrator's from outer space?
Olivia: Erm, probably not.

Nina: Walter, it was never your intellect that made you exceptional. You're brilliant, of course, but it was your imagination, your boundless creativity. Yes, you're not quite whole, Walter, but the best parts of you remain, so focus on that.
Walter: What if I fail?
Nina: You won't fail, Walter.
Walter: How can you be so sure?
Nina: Because you can't.

Peter: What exactly am I looking for here, Walter?
Walter: Anything related to gravity. I remember seeing a file on floaters in there. It would have been from a period when Belly was in search of the perfect bowel movement.
Astrid: Charming.
Walter: Everybody poops, dear.


  • The Observer is among the crowd outside the Massachusetts Metal Depository, standing across the street and using an umbrella.
  • Osmium is not the heaviest element, it is, however, the densest.


  • Peter Bishop states that the element lutetium is "extremely dense" and has a density "just like" osmium. In fact, lutetium's density is less than half that of osmium and is similar to many other elements including lead, silver and gold.
  • When Dr. Krick talks with his son in jail, the horizontal grid changes position every time the camera changes.
  • Counter-weight boots were supposed to pull the thieves down when they stood up, the surviving thief however was able to sit in his car without floating when the boots were not pulling his weight down.


  • "Strange Brew" by Cream
  • "Thunder Island" by Jay Ferguson


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