Katherine McNamara warns that 'darker forces' will tempt Mia Queen on The Flash

Seeing that The Flash's "Armageddon" event was partially inspired by the Arrowverse crossover "Flash vs. Arrow," it wouldn't have felt complete without an appearance from the Green Arrow. Thankfully, Katherine McNamara's Mia Queen finally grapple-arrows back into the action tomorrow night in the fifth and final hour of the CW series.

The last time we checked in with Oliver Queen and Felicity Smoak's daughter was in Arrow's series finale, when she attended her father's funeral in the year 2020 before returning to 2040 to find her brother William, who was kidnapped at the end of the backdoor pilot for Green Arrow and the Canaries.

While the CW ultimately decided not to move forward with that potential spin-off, Mia's arrival in "Armageddon Part 5" does address some dangling threads from the show as the verdant hero helps Team Flash in their last battle with Reverse Flash (Tom Cavanagh) and Despero (Tony Curran).

Below, EW chats with McNamara about her long-awaited return to the Arrowverse, how Mia fits into "Armageddon," and more.

ENTERTAINMENT WEEKLY: The CW decided not to move forward with Green Arrow and the Canaries last year. How did it feel to then get the call that they wanted to bring Mia back for "Armageddon"?

KATHERINE MCNAMARA: It was a huge honor, to be honest. You know how much Mia has meant to me over the years, and how much being a part of this whole world has meant, and how many wonderful things it's brought into my life. I was so thrilled they asked me to come back, especially for something like "Armageddon." There were so many unanswered questions in Mia's story and so many things that we set up, and the fact that [showrunner Eric Wallace] and the rest of the team wanted to give me the chance to come back and answer a few of those questions and give folks a glimpse at where Mia is two years later was a huge gift.

Before the call came, though, had you given up hope of ever playing her again, or were you still holding out?

Obviously knowing that in this world if you're not dead on the slab there's always a chance you could come back, I held out hope. I have had nothing but wonderful experiences working in the Arrowverse, and again, Mia is a character carrying on this legacy of the Green Arrow, and there was always an inkling in the back of my head that there would be a chance to do something just like this. They haven't killed me yet, so I'm hoping there's potential for more in the future.

How did it feel to step into Mia's shoes again after two years away? Did you do anything special to find the character again?

Well, it all started off [with] a wonderful Zoom call with Eric Wallace, and he broke down for me everything going on in "Armageddon," and where they were, and what they were thinking for this episode. I was so floored and flabbergasted in the best of ways at how eloquently and passionately he spoke about Mia, and how much they had absolutely nailed everything she was feeling. I thought they were exactly on point — and on target, if you will [laughs] — as to where she's headed and where she's been and where she would be mentally and emotionally.

Then getting on set and putting on the suit for the first time again, it was really moving. It fit like a second skin, and it really did feel like coming home. I think so many of us over the course of the pandemic have felt as though something is missing in our lives, whether that's social interaction or family or friends. And I felt all those things too, but there was something about getting back in Mia's boots and suit and being back on set that made me realize, "Oh, this is what I've missed for the last couple of years. This is the piece of my life that makes me feel like I'm where I belong."

So putting the Green Arrow on again was all it took to get back into her headspace?

Yeah. I was a bit trepidatious going back. I haven't been in this sort of a schedule in a long time, and I know how quickly these shows run and how hard everyone works, and I used to be such a machine in that system. [So I wondered], "Am I going to be able to snap right back?" And I did. I felt as though I had some sense of normalcy, and there's something about the set of a show like this that is so wonderful. There's such a camaraderie with the crew and cast as we're all getting through things together and making it happen and building the story, and it was so joyous for me. I felt like I was skipping around set all day long.

How does Mia fit into "Armageddon, Part 5"? What brings her to 2021?

A lot of things. There are many, many unanswered questions that we set up at the end of [the] "Green Arrow and The Canaries" [backdoor pilot], and one of those is William [Ben Lewis]. William has been kidnapped. Mia made a promise to Oliver [Stephen Amell] on his death bed that she would protect her brother and take care of the city and her family, and she is at a point where she feels as though she hasn't done that, and a large part of that is William. As we know with Mia, when she gets an idea in her head, she's like a dog with a bone and will not let it go. She has become obsessed with finding William, and that has been her sole driving force, and as with any good Green Arrow, she's coming to that precipice where she's beginning to have to face the question, "What am I willing to sacrifice and compromise in order to accomplish my goals?"

"Green Arrow and the Canaries" kind of combined the post-"Crisis on Infinite Earths" version of Mia — who grew up comfortably, was relatively well adjusted, and had social skills — with the more hardened fighter we met in the pre-"Crisis" flash-forwards. What version of Mia do we get here?

That was my first question as well, and the answer, at least where I was coming from, is that it is the blend, because to me that's my favorite version of Mia. She has the most tools at her disposal and the most weapons in her arsenal, as it were. She not only has all of the Nyssa al Ghul fight training and the experiences she had with her father before "Crisis" and with her mother, but she also has the experience of growing up knowing what life is like in a happy Star City, and she has the social skills and the awareness to continue that.

Now, at the point we find her at, she has let a lot of the new Mia go by the wayside, because she's gone rogue in a way and become very vulnerable and very open to some darker forces and some darker influences, because she feels as though she failed not only the city and William, but her father and the legacy that has been placed upon her. At the point where Mia had Green Arrow thrust upon her, she didn't necessarily feel as though she was ready or worthy for it because she had had so little experience and was just barely beginning to understand why Oliver made the choices he did and what brought him to that place. But now more than ever in this episode, whether or not she realizes that, we see her becoming a Green Arrow that her parents wanted her to be, all with the help of Uncle Barry [Grant Gustin] and Aunt Iris [Candice Patton].

What is Mia's dynamic with Team Flash like? Who does she get on with the most?

I love her dynamic with Team Flash. The strangest [thing was that] the members of Team Flash that Mia would relate to the most are not necessarily the ones she gets to interact with in this episode, but that being said, there's no one who knows Oliver and Felicity [Emily Bett Rickards] better than Barry and Iris. They know not only her parents, but Mia and what her tendencies are going to be given her parents' history and everything all of them have been through.

Barry was right there with her throughout the entirety of "Crisis on Infinite Earths," so he saw firsthand the heartbreak and struggle it took to get through that and move forward. They're right there with her and understand the struggle she's going through of fighting to get her family back and for what's right, but also having to maintain the integrity of being a hero and what that means and the sacrifice that entails. It may not be what she wants to hear, but it's exactly what she needs to hear, and having some really lovely moments with both Iris and Barry throughout the episode and with Reverse Flash and Damien Darhk [Neal McDonough] perhaps... it really is such a well-rounded episode. I think they did such an amazing job of giving Mia a full story, even though it's only one episode.

Eric told me he wanted "Armageddon" to open the door for you to return in the future. Is that something you would be open to doing?

I would love nothing more than to come play in the Arrowverse again. Truly, if anybody needs a gal to come shoot some arrows at some bad guys in a cool supersuit, just cast a green arrow in the sky and I'll come running. That was the biggest gift, I think, on this episode: that we didn't know whether Mia could come back or what happened or where the mythology stood on that, and Eric and the Flash writers were so wonderful to leave that door open and to make it possible for her to be a part of this world again. It's really an honor, and now maybe there's a potential for a future there.

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

This interview has been edited and condensed for length and clarity.

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