The episode explores themes of and vulnerability . Without their advanced technology or the ability to communicate, the team is forced to rely on their wits and their trust in one another to survive a threat generated by the very home they are trying to protect.
Stuck in a transport room, they must find a way to bypass the lockdown manually. [S4E13] Quarantine
As the lockdown progresses, the city initiates a fail-safe that begins to vent the atmosphere in certain sectors to "purify" the air, putting the lives of everyone onboard at risk. Themes The episode explores themes of and vulnerability