When faced with a zombie apocalypse, it becomes pretty clear that you have to rely on the people closest to you. But for the core characters on Fear the Walking Dead, the people closest to them might not be as reliable as one would hope.

While the first episode spent most of its time introducing characters and exploring whether or not the walker that heroin addict Nick (Frank Dillane) saw was real, it also established the tense dynamic that exists as high school counselor Madison (Kim Dickens) and English teacher Travis (Cliff Curtis) try to blend their families. On Sunday's episode (9/8c, AMC), those tensions grow even more when Travis sets out to find his ex-wife Eliza (Elizabeth Rodriguez) and their son Christopher (Lorenzo James Henrie) and Madison's daughter Alicia (Alycia Debnam-Carey) has to babysit her brother as he deals with withdrawal symptoms.

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"For Alicia, a lot of the attention is on Nick," Debnam-Carey tells TVGuide.com. "It's always about how to make this family whole again. In Alicia's mind, this family stopped being whole a long time ago. Once everything crumbles, you realize that the people around you are really all you have. But there's not a lot of trust going on in this family."

The trust issue works against Travis, whom Debnam-Carey describes as just the latest of Madison's boyfriends since Nick and Alicia's father died seven years before. While the lack of a father figure played some role in Nick's addiction, it also forced Alicia to grow up faster than she might have otherwise. "She's had to become self-sufficient at quite a young age because of the absence of her father and the absence of her brother," Debnam-Carey says. "I think it's always been in her to try to get out of that sh---y situation. She has decided to have a plan and leave and has hope for her life and actually wants to do something. But the world is going to crumble pretty quickly for her and leave her with a lot of hopelessness."

Indeed, in Sunday's episode, the police response to the infected people turns Los Angeles upside-down and eventually leads to riots. But out of the chaos springs forth a Madison who is willing to take charge — and get her hands dirty. "The first instinct of our characters isn't to grab a heavy object and bludgeon these people," executive producer Dave Erickson says. "It's a place we have to build to. ... But [Madison] is somebody who will get up to speed relatively quickly. She is very approachable and has a very maternal quality, but she's also a badass. We may see a woman who is more equipped for what's to come."

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The same can't be said for Travis. "What I love about him is that he doesn't fall and crumble and wonder what to do," Curtis says. "He doesn't become violent and erratic, he just stays steady - he stays the course. He remains optimistic, to a point where it could be detrimental. He's insistent about what's good in humanity and good in people and [that] wanting to protect that is something worth fighting for.

"His weapons of choice are a clear mind and a strong, good heart," he continues. "He's going to be the guy on the way out of a burning building who goes to grab his favorite book rather than some implement to start stabbing people in the head. [He's a] man who might not have a place in the new world order, and he might not be willing to give up the things he believes in most in order to change. His trajectory is a sustained resistance to the impending reality. He's not going to cave."

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The differences between Madison and Travis are underlined even more once Travis' ex-wife Eliza enters the picture. "They probably should have never been married, but they did and they did the best that they could," Curtis says of Eliza and Travis. "The relationship expired, and there's no question that they should or shouldn't be together. But when you've been together for over a decade... you know each other well. So within the context of the apocalypse, they function really well together. Travis and Madison are still getting to know each other in an extreme environment and are like, 'Whoa — who are you?'"

And that realization will only grow stronger as the season goes along. "By the end of the first season, [Madison and Travis] will be unrecognizable to each other," Erickson says. "They will both embrace or not embrace the apocalypse in different ways. ... One of them is going to get it a lot sooner than the other, and that will lead to a great deal of friction and a fracture."

Fear the Walking Dead airs Sundays at 9/8c on AMC.

Additional reporting by Hanh Nguyen