“274” is episode three of season one of Helix.
Dr. Peter Farragut, infected by the virus himself, had started infecting others on the base too.
At the end of the previous episode”Vector” (or that episode combined with the first, “Pilot”, in a feature length episode), he caught Julia (his ex-sister-in-law) in the shower and possibly infected her too. When she comes around after the attack she claims not to know what had happened, but she may be covering things up.
At the beginning of this episode Peter approaches his brother, asks for help, and then collapses. He, and the rest of the infected, are going to be held in a former nuclear fusion test area of the base.
This sort of plot is normally something down quite quickly in a film, which imparts a fair sense of urgency, but it’s being handled much more slowly in this, and with consequently less urgency.