The Flash boss says 'the world will end if Iris doesn't step up' in 'Armageddon'

If The Flash's upcoming five-part event "Armageddon" is the worst day of Barry Allen's (Grant Gustin) life, then you better believe that's also true for his wife Iris West-Allen (Candice Patton).

"There's a reason Barry is having his worst day and of course [the question becomes], how does that affect his marriage?" showrunner Eric Wallace tells EW. "That's the second biggest storyline in 'Armageddon': the personal Armageddon of marriage. The love between two people, regardless of your gender or how you identify, how do they survive the end of the world?"

In "Armageddon" — which launches the CW superhero drama's eighth season and features several Arrowverse guest stars — the powerful telepathic alien Despero (Tony Curran) travels to Earth on a dangerous mission that heralds a cataclysmic event and puts him in direct conflict with Team Flash. In fact, Despero has a very specific bone to pick with Central City's speedy hero.

"[Despero] shows up with this pretty foreboding news that there is not only an Armageddon coming, but Barry is directly responsible for causing it," Gustin tells EW. "Barry understands the stance he has and why he's here to speak with him, but Barry is also trying to convince him that it's just not possible he would ever do anything that would cause an Armageddon. So, it's not only a physical challenge, but a mental challenge for sure dealing with Despero."

To defeat Despero and prevent the eponymous cataclysm, Barry enlists the help of several heroes like Black Lightning (Cress Williams) and the Atom (Brandon Routh); however, Barry will need Iris, too. Just look at the place of prominence she occupies on the team-up focused poster for the saga.

"There's a reason why Iris is on that poster," says Wallace. "She is so integral to this story, especially when it gets to the big twist in the middle. Barry can't stop 'Armageddon' without his rock and lightning rod, Iris. The world will end if Iris doesn't step up and she does — and in the most emotional way possible."

The producer was very impressed by Gustin and Patton's performances across the five episodes.

"There's some pretty meaty scenes going on here. It's just a joy to watch Grant and Candice still, eight seasons in, giving it their all, fully committed to the roles, and making magic on screen," he says.

Danielle Nicolet, who plays Cecile Horton, also gets a moment to shine in "Armageddon." Given that Despero has psychic powers, it would be impossible to tell this story without him crossing paths with Team Flash's resident empath.

"Let's just say that when two people with empathetic or telepathic powers meet, somebody will win and somebody will lose, and we don't back away from that," Wallace teases. "Cecile, I'm happy to say, has quite an exciting story in the middle section of 'Armageddon.' I'm not going to go into details, but I just watched a cut of one of the episodes in particular and I would dare say that Dani Nicolet gives a performance of a lifetime over the course of this thing."

"Armageddon" will also feature appearances from Javicia Leslie as Batwoman, Arrow's Katherine McNamara as Mia Queen, Supergirl's Chyler Leigh as Sentinel, and "Crisis on Infinite Earths" actor Osric Chau as Ryan Choi. Tom Cavanagh and Neal McDonough will appear as frequent Arrowverse baddies Reverse Flash and Damien Darhk, respectively.

The Flash airs Tuesdays at 8 p.m. on the CW.

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