Sheila (Drew Barrymore)and Joel (Timothy Olyphant) have faced their fair share of threats on Santa Clarita Diet, but a new couple could be their biggest one yet.

Paul (Zachary Knighton) and Marsha (Jee Young Han), the mysterious duo who have been shadowing the Hammonds as they uncover the origin of the zombie outbreak in Santa Clarita, are getting uncomfortably close to the truth. And now that they've destroyed the cause of Sheila's condition — those strange red clams found off the coast of Serbia — they're setting their sights on the undead, which spells bad news for the Hammonds.

"It is a storyline that we will track into the third season," executive producer Victor Fresco told TV Guide. "They're a threat to the Hammonds. They don't know who the Hammonds are yet and the Hammonds don't know that they're out there, but we know that these guys are gonna want to kill them — or at least kill Sheila."

As a descendant of the Knights of Serbia, an elite group of trained assassins who helped stop the first zombie outbreak 500 years prior, Paul has been charged with a sacred duty that he must fulfill with some help from his wife Marsha, and they won't be alone. According to Fresco, we'll see others like them in Season 3 who aren't exactly skilled killers but will still try to carry out their important mission.

"[Paul and Marsha] are kind of a threat to [the Hammonds] but they're also not like seasoned assassins. Paul runs like a surf shop or vegan restaurant. He's not a trained killer but he is part of an organization that, when called upon, can be activated," he added. Given that they've been tracking the root of the zombie outbreak in Santa Clarita, it's safe to say they've been activated — which doesn't look good for the Hammonds.

However, this secret organization will be just one of the major problems for Sheila and Paul in Season 3. They'll also have to deal with Anne (Natalie Morales), the sheriff who knows they are behind the local murders but, thanks to a perfectly-timed explosion Anne mistakes as a sign from God, she now believes they're killing people for a divine cause.

"It's a delicate thing for them to navigate," Fresco explained. "She thinks they're doing God's work because they're killing bad people and she's seen enough weird signs that she thinks it is a miracle. She doesn't know that Sheila is eating people so it'll be a tricky thing for the Hammonds to navigate how much they let Anne in their lives."

Despite the risk of Anne figuring out the real reason they're murdering people, having a sheriff on their side could come in handy. The Hammonds will need the help of a law enforcement insider now that their daughter Abby (Liv Hewson) has blown up a massive billboard advertising fracking with the help of Eric (Skyler Gisondo) and some C4.

While the teen activists succeeded in destroying the anti-environmental message, their delinquent act will also come with some unintended consequences. "There's going to be some ramifications for what they did. It's going to bring scrutiny into the area because that's a big thing that she [and Eric] did," said Fresco.

Season 3 of Santa Clarita Diet is currently in the early stages of production. Meanwhile, Season 2 is now available on Netflix.

Drew Barrymore and Timothy Olyphant, Santa Clarita DietDrew Barrymore and Timothy Olyphant, Santa Clarita Diet