Os (Fringe)

The episode centered on the Fringe team's investigation into a series of robberies of the element osmium, which they connect to a scientist (Alan Ruck) who is able to defy the laws of physics.

The Fringe team is called to the scene of a robbery of a metal depository; the body of one of the thieves, shot by a security guard, inexplicably floats off the ground, while a second culprit has gotten away.

Walter, who has lamented to Nina Sharp (Blair Brown) his need to have William Bell (Leonard Nimoy) 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.

Simultaneously, Peter (Joshua Jackson) has decided to open up to Olivia (Anna Torv) and shows her the five data discs from the shapeshifters he killed after the doomsday device weaponized him.

[5] Garcia, who previously starred as Hugo "Hurley" Reyes from J.J. Abrams' Lost, appears as a Massive Dynamic guard that is smoking a bong with Walter at the start of the episode.

Club's Emily VanDerWerff graded the episode with a B−, explaining that unlike Tucker, she thought the idea of "soul magnets" was "just so goofy that it's almost too much for me to handle".

Writing for the Los Angeles Times, critic Andrew Hanson referred to audiences' Friday night plans away from television when he commented the episode was "better than any movie you're going to see in the theater right now".

[15] IGN's Ramsey Isler rated the episode 8.0/10, explaining he enjoyed the "classic Fringe" opening scene, the "decent [acting] job" by Ruck, and John Noble's performance; he also thought the script was "very clever [as] it reveals surprising story elements with innovative tricks".

[16] Billy Grifter from Den of Geek was slightly disappointed with the "mad scientist" storyline as he felt it had been done before, but found several redeeming qualities: Alan Ruck's performance and the last five minutes featuring Noble and Blair Brown, and Torv with Joshua Jackson.

[17] Referring to Torv's "passable" Nimoy impression, Grifter concluded that "the strength of Fringe is that it can take a rather light and fluffy premise, like the one in "Os", and embellish it with wonderful character moments and a genuine surprise or two".