S.H.I.E.L.D. is called in to investigate the mysterious murders of a pair of volunteer firefighters, both of whom were in the city during the Battle of New York, who were killed by an unexplained powerful electromagnetic field that started inside their bodies and left their corpses hovering in mid-air. Coulson (Clark Gregg) and his team track down another member of the squad suffering from the same infection caused by a Chitauri trophy.
Unable to save the third victim, Coulson orders Simmons (Elizabeth Henstridge) to work on a cure for any of the other firefighters who may have been infected. But while the team is en route to the Sandbox to safely dispose of the helmet, Coulson notices that his scientist has been infected with the virus. Ordered to “dump infected cargo,” Coulson refuses to comply to a direct order, and he’s not the only one as Fitz (Iain De Caestecker) risks his life to join Simmons in quarantine to help create an antiserum. Eventually it takes the work of both scientists and Ward (Brett Dalton) to save Simmons who decides to follow protocol and sacrifice herself rather than allow any of her friends to come to harm.
Although the mystery of the odd deaths is short-lived, Simmons’ infection plays well (especially given executive producer Joss Whedon‘s history of killing of characters). The episode’s B-story continues the tease of something being wrong with Coulson, although this time from his perspective as he orders a full physical and blood work after becoming acutely aware of something being “off.” Melinda May‘s (Ming-Na Wen) explanation for the change in Coulson is certainly plausible, but we’ll have to wait and see if there is indeed more to the story. It’s also worth mentioning the oddly ominous beat after the rather sweet moment between Fitz and Simmons to close the episode which appears to be another aggressively-obvious use of foreshadowing (one of the show’s definite weak-points) to point out an issue with one of the scientists down the road.