In the Season 8 Contagion two-part event, the firefighters of Station 118 respond to a fire at a biomedical research lab where experiments on Crimean-Congo hemorrhagic fever have gone horribly wrong. An unstable scientist named Moira steals both the accelerated virus strain and the only known antidote, then triggers a facility emergency and an explosion traps key 118 members deep underground with the virus now in the air.

Bobby Nash, Hen, Chimney (Howard Han), and Ravi are caught inside the lab after emergency lockdowns lock them in. Hen suffers a collapsed lung, and Chimney’s protective mask cracks, exposing him directly to the highly lethal virus, which is described in-show as capable of causing severe hemorrhagic fever and rapid, dangerous progression of symptoms.
Outside, military forces cancel a planned extraction once they learn how fast the virus spreads. As U.S. Army official Colonel Hartman puts it, they now have “a pandemic in a bottle” and refuse to risk an uncontrolled outbreak.
Bobby and Ravi find the lab’s only supply of the antidote, but Moira has taken it with her when she fled. In a heartbreaking moment, Bobby tries to convince Ravi to use it on himself, but Ravi insists Bobby go first, a decision that dramatically shapes the cliffhanger.
The episode ends with Chimney growing visibly worse, coughing blood and struggling with the infection, and Hen still seriously hurt, while the fate of the trapped heroes remains uncertain. A preview for Part 2 shows Athena and Buck attempting to get the antiviral into the lab as Buck and Hen scream in anguish, hinting that someone may have already died or is on the brink of it.
What Happens To Chimney, Hen and Bobby?
By the end of the virus cliffhanger, all three are still in immediate danger: Chimney is already showing serious symptoms from the exposure with no treatment within reach, Hen is badly hurt and fighting to hold on, and Bobby has effectively given up his own shot at the antidote so someone else might survive.
This cliffhanger capped Part 1 of the arc, leaving fans anxiously awaiting Part 2 — where the key questions are whether the antidote can be delivered in time, who survives, and how the 118 deals with the fallout of Moira’s actions.

