Plus, Gugu Mbatha-Raw, David Oyelowo, Jessica Plummer, and Ben Hardy reveal who they thought the culprit was.

Warning: This article contains spoilers about the finale of The Girl Before.

Even the cast of The Girl Before didn't see that ending coming.

At the end of the four-episode miniseries (streaming now on HBO Max), Jane (Gugu Mbatha-Raw) learns the truth about what happened to Emma (Jessica Plummer) in the house. Though it wasn't an accident, Edward (David Oyelowo) — despite being extremely controlling and intense — had nothing to do with it. Instead, it's revealed that Emma's ex-boyfriend, Simon (Ben Hardy), pushed her down those deadly concrete stairs in a fit of jealous rage. In the present day, Jane finds herself in a similar situation when she realizes what Simon has done. After a final violent confrontation, Simon finds himself dead at the bottom of the stairs, in much the same way his victim did.

Jane decides to be open with the police about what really happened, both for her and for Emma. And instead of going through with the abortion as Edward desired, she decides to keep the baby to raise on her own, and leaves things (possibly) open for a future with Edward — provided he seeks help for his repetition compulsion.

Ahead of the finale, EW caught up with Oyelowo, Mbatha-Raw, Hardy, and Plummer to dissect the twisty ending, the work they did with various consultants to give justice to their characters and their traumas, who they thought the killer was, and more.

ENTERTAINMENT WEEKLY: The show deals with some very heavy topics — rape, stillbirth, death, violence, grief — and there were a lot of consultants involved in the making of the show. What did you find most instructive for bringing your character and their trauma to life?

GUGU MBATHA-RAW: Well, for Jane, I think what really rooted it all for me was the psychology of what she's been through, which is a stillbirth. That's very heavy subject matter to research, but I think we were all very keen to respect the experience and the material, and try and make it as authentic as possible whilst somewhat still in a genre piece. We were able to partner with Sands, which is an organization which helps people processing the grief of stillbirths. And I was able to speak with a bereavement midwife, which was incredibly instructive and very sad, but it's amazing work that they do. In terms of Jane's memory box, which we have in the show, which is her memories of Isabelle, her daughter, everything that went in that box was all meticulously researched. And I spoke with a therapist, and also a friend of mine who has experienced a stillbirth herself, who was very generous to share some of her experiences with me.

DAVID OYELOWO: I spoke to a therapist as well, and Edward has something called repetition compulsion, which is a condition that we all have to a greater or lesser degree, in a sense, whereby you're trying to fix things that have went wrong, and you're sometimes making the same mistakes again and again and again. Taken to an extreme, it's people who literally try to orchestrate the same circumstances, but if we're all completely honest, we do that to different degrees. I also spoke to an architect, or a "starchitect" as they are often called — these sort of high-powered architects who make these celebrated buildings. And he did confirm that there is a controlling mentality, to have that much power in terms of these massive structures that go up, that take thousands of people to build. Directors have this as well, by the way — not [our director] Lisa Brühlmann — and anyone who is the captain of a large ship can be susceptible to this kind of behavior, and Edward is definitely that.

JESSICA PLUMMER: I worked with a load of people that gave me support in the prep for playing Emma. A therapist was one of them, who is a specialist in that specific trauma that Emma went through. And it was incredibly insightful just in terms of answering the questions that I didn't know the answer to. Like, why wouldn't she leave? Why didn't she tell the police? And just being able to get those answers. And I think what I learned is that the main thing that Emma is carrying is shame and guilt because she blames herself. I don't think Emma even considered it a rape necessarily because she felt like, "I put myself in that situation, so it's my fault." I think so many women in similar situations don't speak out or say anything because of that, because of the fact that they feel like it's their fault. So, just having questions that I didn't know the answer to answered, and [learning] coping mechanisms and the real conversations that someone in Emma's position who was also having therapy would have, was all incredibly insightful.

The Girl Before
Ben Hardy and Jessica Plummer in 'The Girl Before.'
| Credit: Amanda Searle/ HBO Max

Ben, how did you tap into the mind of a killer?

BEN HARDY: I will say that my fear in playing Simon was that it is very dark and very twisted playing someone who some people consider to be psychopathic. I personally don't think he's psychopathic, but I don't know. So much of my preparation was [seeking to understand him]… I can't play someone if I think them to be entirely evil. Look, I can objectively say he was in the wrong, but throughout filming, I had to think of it as, "This is what logically makes sense, because this logically made sense to Simon." I know how insane that sounds, but that kind of brings me to my point. I was worried I was going to drive myself insane doing these mad journalings of Simon's logic. His trauma is the breakup and what that does to him, and his way of trying to control the situation and bring it back is clearly not the best route, and not one I would ever advise anyone to do, but it was interesting to explore that. And I did also talk to a therapist to try and get inside his psychology and learn what could lead someone to do that. What could have happened in their upbringing? What could lead them down that road? Because I do like to think that for a lot of us, we have a certain amount of control within our lives, but also what happens to us can also really deeply impact us and deeply affect us and lead us down roads we don't want to actually go down, potentially. So, I was trying to sympathize with that.

Were you guys surprised by Simon being the killer? If so, who did you think the killer was instead?

MBATHA-RAW: The thing I loved about the show is that I was constantly guessing about Edward, and I would keep changing my mind, and I'd be like, oh, he's just a genius. And then I'd be like, oh my God no, he's definitely sort of bad. And I think that's the thing about the show, is that nobody is a hundred percent good or bad. You start ending up sort of understanding them as human characters. So I loved being kept guessing and I totally didn't see it coming with the character. Not like this.

OYELOWO: The joy of a thriller is that you know that where your nose is being pointed towards is probably not the place the answer is going to be found. But then, like I remember seeing The Undoing, and thinking there's no way it's Hugh Grant. They managed to make that be the reason that you were wrong-footed there. So weirdly, seeing that show actually threw me off really. I think I thought it was [Edward's business partner] Peter Creed [Ben Addis] for a while when I was reading this. My wife, who is the person who knows who the murderer is within the first 30 seconds of a show, didn't figure it out. So that, I think, is a testament to the writing.

PLUMMER: In the audition, you get an email from your agent and it kind of gives you the breakdown of what's going to happen to your character, so I knew something bad was going to happen, but I didn't know who, what or how. And I did not see that coming at all. Who did [I think did] it? I'm not quite sure, maybe the house could have done it. It could have just been an accident.

HARDY: That would've been such a dud of an ending, though. Oh my god.

Do we think Simon's done something like this before, or he just snapped?

HARDY: I will tell you his backstory right now, real briefly. I don't think he'd ever done this before. I don't even know if I've told Jess [Plummer] this, but I think his mother left his father for another man and he always saw his father as an embarrassment, and his whole life, he was like, "I'm never going to let that happen to me. I'm never going to be cuckolded," essentially. "I'm going to find this perfect woman and I'm going to hold onto her," and he's found her. And then, the very thing that he spent his entire life trying to ensure would never happen, happens to him, and he physically cannot allow that to be. And so for him, when he goes there to try and win her back, that's why he's going. That's why he's, in this weird, controlling, manipulative way, kind of trying to create this situation where she sees how amazing he's been to her. And when he's there in that final moment, he's there to win her back. But it becomes abundantly clear that's never going to happen, and then he snaps.

The Girl Before
Gugu Mbatha-Raw and David Oyelowo in 'The Girl Before.'
| Credit: Amanda Searle/ HBO Max

Gugu and David, how did you guys feel about Jane telling Edward to get therapy at the end there? Do you think there's a future for them?

MBATHA-RAW: The idea of the therapy, I think, was somewhat of a departure from the original [book]. And I think what I thought was interesting about that is, that we are again showing the potential for growth and evolution and hope for these characters, and that we are not just condemning them to being good or bad, but just human and complex. And that, to me, was really interesting. And I think for Jane to be able to sort of make that choice to move on with her life, but the door's not completely been slammed shut with Edward, there's potential and there's hope, but I think on terms that are going to take a lot of work. There's definitely nothing tied up in a bow in this, so I think that I appreciated that because I thought that was refreshingly real.

OYELOWO: So did I. I mean, he made a step that is kind of surprising in going to the therapist, but also we made this 11th hour choice to show the house being shown to another potential tenant. So it's like, did he learn the lesson? Is he looking for another Jane or Emma, as it were? But I am banking on the sequel, which will be The Girl After The Girl Before. And Gugu and I are going to go at it all over again. [Both laugh]

Jessica, do you feel like justice was done for Emma in the finale?

PLUMMER: Absolutely. So when we were shooting, I know that quite a few different versions of an ending were shot. Also, I remember getting different versions of the script and there was constantly changes happening. And whilst we were shooting it, I didn't ever read Jane's storyline. So the ending for me, when I was filming, was when Emma died. So, watching it as a viewer, all pieced together, and then seeing everything that happens with Jane and Simon and then Edward and Jane wanting to get justice for Emma, and then at the end with the crystal on the picture frame with her son… I mean, all of it, I was weeping near the end. I definitely feel like Jane got justice for Emma, for sure.

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

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