Last night on Fringe, as the show opens, a man gets off an elevator when his nose begins to bleed and within moments  he passes out. Then, a bike courier tries to give him CPR but his veins begin to bulge and break, spraying blood everywhere.

Olivia and Peter start the investigation while they wait for the rest of the team to arrive. While they are upstairs questioning witnesses, Walter and Broyles stand outside when suddenly the bike courier dies in the front lobby. They quickly realize what caused both deaths is a deadly virus which is contagious, and looking for a host.

They have to quarantine the building with Peter and Olivia still inside. As the day goes on, the virus keeps contaminating people and causes violent reactions among the victims before they eventually die.

Walter and a team of CDC agents finally enter the building in hazmat suits to try to get the uninfected people out. Olivia and Peter are cleared, but as they are about to leave, CDC agents realize Peter is infected too so he has to stay in the building with the others whoa re infected.

Knowing that Peter’s life is at stake, Walter works frantically until he discovers the antidote to the virus which is made up of household items. Walter figures out a solution to kill the virus, but they can’t get close to the infected people because they have become unruly.  As a last resort, Olivia goes back into the building and activates the ventilation system with  fentanyl gas that knocks the victims out. They are then able to give them all the antidote and everyone, including Peter, is saved.