Jesse, Joey, Justine and Olga wake up in what appears to be an abandoned prison. With Joey, Justine and Olga locked away in jail cells, Jesse must quickly find a way to free his friends so they can escape the cell block.

The team is still trapped in the cell block, but Jesse has found the key. While opening the cells, he accidentally releases a dangerous Alpha Zombie into the open, who proceeds to wreak havoc on his team.

A second team (Iman, Sam, Meghan and Jeana) wake up in the medical wing of the prison. On top of being surrounded by a zombie hoard, they discover that they are locked in a room with two zombies. They must find a hidden key and escape before time runs out.

Team 1 has been locked away in a pitch-black room. When the lights come on they realize they have been captured by a mysterious paramilitary organization. With the help of Doctor Altagracia on the radio, team 1 must escape their captors, and get to the main courtyard of the facility.

Team 1 makes it out of the facility, only to find the way to freedom blocked by a courtyard crawling with zombies. Meanwhile, team 2 has escaped the infirmary, and must make their way to the Bio lab on the 3rd floor to create the antidote.

Team 2 enters the Bio Lab and proceeds to mix together part 1 of the antidote.