Season 1

Sierra, dressed in a bloodstained Hazmat suit, cautiously navigates a seemingly-abandoned military camp where a dead soldier is slumped up against a truck and a burned out tent is still smoldering. Sierra catches sight of an injured Gabi hobbling through the camp when she is suddenly attacked by two zombified soldiers.Meanwhile, Gabi briefly hides behind a vehicle before running off once again.

Aware of the fact that Gabi is spying on her, Sierra dresses a walker up in her Hazmat suit and uses it as a distraction to ambush Gabi. Sierra wants to know why Gabi is following her. Gabi admits to following Sierra and it was because Sierra could kill the infected and she (Gabi) could not. Sierra then uses Gabi as a shield to take down the infected in the Hazmat suit. Sierra begins to walk away, but Gabi pleads with her not to go. Sierra enquires as to how Gabi got her limp, and Gabi admits to twisting her ankle 'on the road.'

Gabi and Sierra enter one of the watchtowers of the military camp and survey the damage. Sierra cleans her knife in the leg of her suit and tells Gabi she has no where to go. Gabi asserts that she does. Sierra isn't convinced Gabi does know a safe place as she would be there already. Gabi says they head south, towards Mexico. Sierra shoots down the idea, saying that the border is crawling with infected as when the infection hit people tried to head both north and south. Gabi assures Sierra that there is a tunnel under the border. Gabi's boyfriend was border patrol and he sealed the tunnel after the infection hit and then went to check it out, with Sierra noting that he hasn't returned. Gabi persists saying that Sierra needs a safe place and that she (Gabi) needs help. Sierra reluctantly agrees, but reminds Gabi that she (Sierra) doesn't need Gabi.

Gabi and Sierra are trudging down a road towards the boarder. They seem to be in the middle of a discussion, but Sierra keeps pulling ahead and tells Gabi to keep up. Sierra admits to being from Los Angeles, California, that she left when the military came, but that it didn't matter because "the bombs followed us." Gabi tells Sierra that "you are not the only one to loose someone." Gabi says that she lost her sister because "I couldn't stop them." Sierra unsheathes her knife and tells Gabi to go for the eye, temple or base of the skull, but be careful not to hit the skull.

Gabi and Sierra enter a construction site. Sierra is wondering how far it (the tunnel) is, and Gabi assures her that it isn't far. They round some construction equipment and are confronted by a chained up infected. Gabi freezes, but Sierra urges her on, telling her that now would be a good time to try out her skills with the knife. Gabi raises her knife, but before she can strike, a gunshot rings out and hits the infected.

The shooter of the chained infected is revealed to be Colton, Gabi's boyfriend. Colton and Gabi embrace, relieved to have found each other. Colton admits he thought he had lost Gabi "when the bombs fell." He enquires after Gabi's sister and Sierra. Gabi say's Sierra is the reason she reached the construction site alive. Colton thanks Sierra and Gabi says her sister is dead because they waited too long. As Sierra picks up her dropped knife, Gabi and Colton embrace again, while Gabi says she and her sister waited because she thought Colton was coming for them.

Colton brings Sierra and Gabi to the tunnel and tells Gabi to go down first. She seems concerned about Sierra, and Colton says he will send her down next as he has to go down last in order to close the tunnel behind them. After Gabi enters the tunnel, Colton faces Sierra and tells her that he is sorry, but he can't take the chance that she will tell anyone else about the tunnel. He raises his gun to shoot, but Sierra reacts faster than he thought he would and she stabs him in the leg. She climbs down into the tunnel while he is recovering.

Sierra descends the ladder into the tunnel where she in confronted by Gabi while Colton keeps shouting from above that the tunnel is unsafe. Sierra tells Gabi the truth-- that Colton tried to kill her. She also tells Gabi that Colton abandoned her and had no intention of coming back for her. Sierra says they have to leave and starts down the tunnel. Gabi stares at the circle of light above and listens to Colton for a moment longer, before turning just as Sierra hits a trip wire.

The tripwire was activated and caused an explosion. Sierra and Gabi wake up with ringing ears, coughing, and covered in dirt.

Colton roughly pulls Gabi and holds her by her face, repeating "Didn't I tell you to wait for me?" They hear Sierra getting up and making her way further down the tunnel.

Sierra limps around the tunnel, coming across a well lit area full of tools and pipes. She hear Colton talking to Gabi behind her, and she frantically searches for a place to hide, almost tripping over tracks built for mining carts.

Gabi and Colton are walking through the tunnel when an unknown voice calls out.

Colton tries to convince Gabi that he wont hurt her and that she needs him. Gabi responds that she doesn't believe him and that she will be fine on her own. Colton, seemingly angry, asks her if she thinks THEY will let her go alive.

A mining cart rattles down the rails, drawing the attention of the border patrol guard who is searching for whoever set off the booby trap. He goes to investigate as a second unidentified border guard approaches.

Colton is still holding his gun on Gabi and tells her "You're not worth it, babe," and he prepares to fire, but is attacked from behind by Sierra and drops his gun.

Gabi follows Sierra to a ladder that leads back above ground, however, they must sneak past a zombie eating one of the dead guards. Meanwhile Sierra slides past, Gabi is nearly grabbed but missed.