After Troy unleashed the massive horde upon the ranch, he and Nick attempt to come up with a plan to rescue everyone.

Meanwhile, Alicia and rest of the ranch members find themselves trapped in the bunker.

Ofelia and Crazy dog end up finding that there is no air being pumped into the room. Alicia reveals that they only have about 2 hours of air supply left until they all suffocate.

Crazy dog an Ofelia decide to go into the air ducts to try and locate and fix the issue, before time runs out. In order to buy them some time, Alicia comes up with a plan to kill anyone who is infected, in order to reduce the amount of oxygen being consumed.

Alicia explains the air situation to everyone and asks that anyone that has been bitten, to come forward.

Initially, no one complies. However, everyone that is infected gradually begin to step forward.

Although reluctant, everyone follows through. Utilizing the medicine at the ranch's disposal, Alicia injects everyone with a dose of morphine. Once heavily sedated, Alicia proceeds to stab them all behind their heads.

Alicia is left shaken and emotional after coming to terms with what she had done. Alicia finds comfort in a woman named  and they confide in each other.

After a while, everyone loses consciousness due to lack of oxygen. Alicia awakens briefly and is attacked by a recently turned infected. She is able barely able to fight her off but she is able to kill the infected, which lands on top of Alicia right before losing consciousness again.

Ofelia and Crazy dog locate and free an infected that was lodged in air circulation vent, which restores the air supply to the bunker.

Troy and Nick make a run to a nearby helicopter,but are pinned down inside by the horde. They are eventually saved by Madison, Walker and Strand who arrive just in time who use the ranch's fuel reserves to set the infected ablaze, along with the ranch.

With oxygen restored to the bunker, Alicia regains consciousness and is able to make her way to the armory. She then begins to gun down all of the infected within the bunker. Just as Alicia is about to be overwhelmed, she is saved by Madison and Nick.

With the ranch lost, Madison suggests they all head back to the dam. Alicia declines after learning of Jake's death and sets out on her own, intent on heading to the place where Jake wanted to run away to with Alicia.

Nick offers to follow Alicia in order to make sure she is safe, and Madison makes Nick promise her that he will return.