First, there was Elliot (Rami Malek). Then, there was Mr. Robot (Christian Slater). But who is the Other One? The Hollywood Reporter speaks with Esmail about the compelling new mystery.

[The following story contains massive spoilers for season four, episode two of USA Network's Mr. Robot, "402 Payment Required."]

It's as Yoda always said: "There is another."

Mr. Robot creator Sam Esmail dropped an enormous bombshell in the second hour of the USA Network's final season — namely, Elliot Alderson (Rami Malek) is not alone. Sure, we knew he was sharing headroom with the titular Mr. Robot, played by Christian Slater, the spitting image of Elliot's deceased father, Edward Alderson. But the episode "402 Payment Required" contains the shocking revelation of a third personality or presence within Elliot — one that has yet to be identified to the audience, but one that has been part of the series' endgame plan from the very beginning.

Some background on the reveal: Elliot spends the second episode of the final season alongside his sister Darlene (Carly Chaikin), the two of them processing the recent death of their mother, Magda (Vaishnavi Sharma). Near the end of the hour, Darlene and Elliot have an emotional breakthrough with each other, and during the conversation, Darlene casually mentions the recent return of Elliot's old nemesis Fernando Vera (Elliot Villar) — the drug lord who killed Elliot's girlfriend Shayla (Frankie Shaw) in season one. Apparently, Darlene had already told Elliot all about Vera's return some weeks earlier. Elliot has no memory of this discussion — and what's worse, Mr. Robot has no recollection of it, either. Cue Elliot's very fair question: "If it wasn't you and it wasn't me, then who was it?"

The scene cuts to a view of the New York City skyline from the same boardroom where Elliot first met Tyrell Wellick (Martin Wallström) at the end of the pilot. A young version of Elliot swivels around in a chair — round and round he goes — with three additional empty seats sitting around the table. Making matters all the more confusing: Elliot's mother walks in — the same version of the woman we and Elliot alike have seen through his own hazy perspective. She and the young Elliot embark on a surreal conversation:

Magda: "I've been looking all over for you. You shouldn't be sitting there, that's not your seat."

Elliot: "Why? I thought …"

Magda: "They're not ready yet. We need to wait."

Elliot: "For what?"

Magda: "For him."

Elliot: "You mean Mr. Robot?"

Magda: "No."

Elliot: "Elliot?"

Magda: "No … the other one."

The boy removes himself from his seat, follows Magda out the room, and that's it — no more information, just a massive question casually dropped into the final stretch of the series, like a cat knocking a precious family heirloom off a table.

So … "the Other One." Who exactly could that be? For years, a contingent of Mr. Robot fans have talked about Tyrell Wellick as a different side of Elliot's personality; their previous interactions both with each other and other characters entirely throughout the series seem to negate the possibility. Are there other players within the Mr. Robot universe who would make sense in hindsight as a separate side of Elliot? Are there hints within Rami Malek's own performance of times where he played a third version of Elliot?

Here's my personal theory: Is it possible that "the Other One" is actually us, the audience? After all, Elliot routinely speaks to the viewer in narration, calling us "friend," calling upon our help from time to time to see things he is not able to see — are we more actively involved in the story of Mr. Robot than we ever gave ourselves credit for? As the series winds down, will we be invited to sit at the table with Elliot and Robot?

It's all speculative for now, but if there's one man who can shine some light on the subject, it's Sam Esmail himself. Naturally, Esmail isn't exactly feeling the need to explain the situation just yet. When I sat down with Esmail for our recent Series Regular podcast interview, the Mr. Robot creator weighed in on the huge "Other One" reveal — though he was as coy as the series itself. Read the following edited excerpt from our conversation and see if you can glean any information for yourself.

"The Other One," Sam? What does that mean?

Wow, we're just jumping in?

Yes!

I'm obviously not going to answer that question!

Obviously, but how long have you been playing with the idea that there's more to the picture than just Elliot and Mr. Robot?

From the beginning.

This is baked into the premise?

Yes. (Pauses.) Sorry, I'm giving you short answers.

That's the level of secrecy you need to keep up on this?

Oh, yeah.

This is a big, final endgame card?

Absolutely. This is the beginning of that big final reveal of the whole series. Honestly, it's one where I haven't quite … you know, I go on the subreddit, I read theories, I listen to podcasts. This is one that hasn't been predicted yet.

That's exciting for you, right?

It's exciting, but it's nerve-racking. I'm curious. If it does get out there, or if people do hit on it — and I do think that once this episode airs, the theorizing machine is going to kick in — I think it's one of those things where if we did our job right, it's a balance of it feeling inevitable, but also unexpected and surprising. That's what we're going for. We don't want it to be too much of a shock where it's just a gotcha and a gimmick type of twist moment. We want it to feel earned. Because the answer should make sense; you guys could technically figure it out because it's been in the show the whole time. We are excited to see it play out.

When the shoe drops, we'll be able to go back through the whole series and see it?

Yes, absolutely. Yeah.

Do you expect it adds a lot to replay value?

Yes. Yes.

I have to do a tenth rewatch?

Yeah!

Don't you know we're in the middle of peak TV?

Just watch it!

What are your theories on "the Other One," Robot nation? Follow THR.com/MrRobot for more clues as the USA Network thriller continues, and if you have not done so already, listen to Esmail's thoughts on the final season in a special edition of the Series Regular podcast: