Warning: Major spoilers ahead for the "Westworld" season two finale, "The Passenger."

After the earth-shaking finale of the second season of HBO's "Westworld" in which Dolores and Bernard successfully infiltrated the real world, an important scene with Emily (Katja Herbers) and William (Ed Harris) ran after the credits for the episode.

The scene shows William, in the future, arriving to a strange and decrepit version of the Forge. He's greeted by a host-version of his daughter Emily, who tells the not-quite-human William that she needs to verify "fidelity."

"I really questioned the nature of my reality," Herbers told INSIDER when asked about her first reaction to reading the scene script. "I questioned everything in retrospect for a second. But, from my understanding, everything that happened between the Man in Black and [Emily] prior was real, and he did kill me."

Katja Herbers as "Emily" on the post-credits scene. HBO

Though Herbers tells me she's not speaking as an authority on the exact parameters of the scene, her interpretation of what that post-credits scene means for William and Emily is vital.

"Here we are sometime in the far, far future where [Emily] is a host and I'm not entirely sure what the Man in Black is," Herbers said. "He might be some other thing entirely."

"Westworld" co-creator Lisa Joy also helped explain this scene in an interview with The Wrap.

"[William] is in a very different timeline. The whole place looks destroyed, and then she explains that all of that stuff happened long ago. That was real. But now something has happened and the Man is now the subject — or some iteration of the Man is now the subject — of testing. The roles have become completely reversed. And we get the feeling that, in the far-flung future, the Man has been somehow reconjured and brought into this world and he’s being tested the same way the humans used to test the Hosts. And that is a storyline that one day we’ll see more of."

So what exactly is going on here? Let's dive in.

Understanding the jump forward in time

As Herbers said, this post-credits scene jumps forward far into the future, after all the other events of season two — including William shooting and killing Emily.

So where did the time frame change for William's scenes? The key lies in the elevator. When Dolores and William confronted each other towards the start of the finale, he shot her several times to no effect, and then his gun backfired on him thanks to the warped bullet Dolores had put there.

William was left on the ground, recovered by the Delos QA team, and brought to the evacuation area (where we see Stubbs look at him laying down on a cot at the end of the episode).

William on the cot on the evacuation beach. HBO

From our understanding, all of those events happened in real life and in the same time frame as the rest of the episode.

The version of William that gets into the elevator and heads down into the Forge is the one which exists in the future.

The editing intentionally showed William entering the elevator with Bernard waiting below at the same single elevator bank in order to complicate the events. But when the elevator arrived for Bernard — it was empty. This implies that the real William was either still on the ground or had already been scooped up by QA. We didn't get a shot of what Bernard saw outside when he left the Forge, so that transition is still a mystery.

William has likely been going through loops to try and find a pathway for himself that doesn't end in the tragedy of Emily's murder

In the future scene, William is likely some kind of host-human hybrid undergoing a brutal loop of his own life and the various pathways he might have taken.

Here's the full conversation that takes place between Host-Emily and Future-William:

William: "Oh fuck. I knew it. I'm already in the thing, aren't I?" Emily: "No. The system's long gone." William: "What is this place?" Emily: "This isn't a simulation, William. This is your world. Or what's left of it. Do you know where you are, William?" William: "I'm in the park. In my fucking park." Emily: "And how long have you been here?" William: "I don't know." Emily: "Tell me. What were you hoping to find? To prove?" William: "That no system can tell me who I am. That I have a fucking choice." Emily: "And yet here we are. Again." William: "Yeah, again. How many times have you tested me?" Emily: "It's been a long time William. Longer than we thought. I have a few questions for you. The last steps a baseline interview to allow us to verify." William: "Verify what?" Emily: "Fidelity."

"Fidelity" is the same term used when younger William met with the host-human version of James Delos. It means they're testing to see if the copied version is a faithful replication of the real person.

Jim Delos in his own fidelity test. HBO

"[Emily is] a host, and who knows what William is, because he's not human," Herbers said. "But we've not seen this world, this post-apocalyptic, far in the future world, right? So, I think what he is might be a little bit more complicated than just a host in him. But, oh jeez, I don't know [laughing]."

The key to understanding how and why this Future-William wound up in that version of the Forge all connects to what we learned about how the Forge tested various human copies in order to replicate the truest version possible.

William murdering Emily is the moment that defines him

The Forge-version of Logan told Dolores and Bernard that the moment which defined James Delos was his final conversation with the real Logan.

"This is the moment that defines James Delos' life," he said. "This was the last conversation Delos ever had with his only son. Logan overdosed six months later. I built Delos a million different pathways. They always ended up right here. This moment."

"You're saying humans don't change at all?" Bernard asked.

"The best they can do is live according to their code. The copies didn't fail because they were too simple, but because they were too complicated," Forge-Logan said. "The truth is that a human is just a brief algorithm — 10,247 lines. They are deceptively simple. Once you know them, their behavior is quite predictable."

Ed Harris as William on "Westworld" season two." HBO

Given this explanation, William's defining moment during his real life was the scene we watched play out on episode nine — when he shot and killed his own daughter.

More evidence of this explanation lives on the HBO website created for "Delos Incorporated." Typing in Charlotte Hale's password used on the first episode of season two (XOmegaCH) brings you to a 3D rendering of the circular room William and Emily are sitting in during the post-credits scene.

There are a series of "log" videos, which show real scenes from the show, that trace William's life. The only video marked with a red circle shows the one of him shooting Emily.

The Delos Incorporated website is a big Easter egg. HBO/Delos Incorporated

The red circle on this event log is a likely marker of it being the key memory for William.

So even though Host-Emily tells Future-William that they're not in a simulation, it seems as though he's definitely undergoing some sort of loop testing — possibly in order to try to find an outcome for his life that doesn't involve murdering his own daughter.

Why this doesn't mean William was a host the whole time

"Not at all. Not at all," Herbers said when asked if this post-credits scene discounts what we thought knew about William and Emily being human in earlier season two scenes. "I don't think so. Just dramatically it would take away the biggest heartbreak you can imagine [when William killed Emily]."

This means the William we saw throughout the season and up until the elevator scene was the real, original William. Him being human for those scenes makes for a more impactful narrative arc. As we saw, the real William was having his own delusions and issues with understanding what was real around him.

He became paranoid to the point of murdering his only child — and that reality is far more impactful if it was a true moment.

Katja Herbers as Emily on "Westworld" season two. John P. Johnson/HBO

"I think [William killing Emily] such a big story moment for the Man in Black — a defining moment for his whole character," Herbers said. "I think it would be really silly if we were hosts. Look, I don't know, but I clearly don't think that's the case. Hand over heart."

In order to become Williams, Emily's death would have to have been a real event between the two people, just as James Delos's key life moment was between him and his real son Logan.

Williams wanted to die permanently and destroy the Forge

William's ultimate desire was to destroy the Forge. Throughout the first and second seasons, William repeatedly said he was going to burn Westworld to the ground, and end his biggest mistake (the Forge) once and for all.

He wanted to ensure that he could die for real, and never be brought back as a bastardized human-host hybrid.

"That’s what you want, isn't it? To destroy yourself?" Dolores asked William on the finale. "But I won't give you that peace. Not yet."

William (Ed Harris) on the post-credits scene. HBO

On the fourth episode of this season, when confronting Major Craddock in Las Mudas, William also spoke about death being the only true thing in the world.

"Death's decisions are final," he said. "It's only the living that are inconstant and waver — don't know who they are or what they want. Death is always true."

After Juliet's death by suicide, William also told the host-version of James Delos that some people are better left dead. "I'm beginning to think that this whole enterprise was a mistake," William said. "People aren't meant to live forever."

But William didn't get what he wanted — and sometime in the future he's no longer human

Because Dolores incapacitated him before he could make it to the Forge, William failed to achieve his one goal.

William spoke to Lawrence on the second episode of the season about his plan. After explaining to Lawrence that the park was designed for people to sin without judgment (despite being secretly observed by Delos), William laid out the bone he has to pick with Ford after being given his profile.

William wanted to contest the profile evaluation Ford gave him. John P. Johnson/HBO

"I have received my judgment all the same Lawrence, and I take issue with it," William said. "Because up until this point, the stakes in this place haven't been real. So I'm gonna fight my way back, and appeal the verdict. Then I'm gonna burn this whole thing to the f------ ground.”

William wasn't able to "appeal the verdict" in his true life. So now, in the future, he's been trying to appeal it again and again. But as we see in the post-credits scene — William is bound to relive his greatest mistake over, and over, and over.

He inadvertently created his own personal hell, one without escape. Over the course of his life, William eventually came to realize that immortality came with too great a cost, but by the time he wanted to roll back the technology he created, it was too late. William helped destroy the last remnants of what it meant to truly be human.

Now it's Dolores and the hosts' turn to try and make a new version of the world. We'll have to wait until season three to see if they'll be any more successful.

Speaking of the third season, it's very possible we'll see the real William's life carry on after he's rescued from the park. Perhaps the future episodes will close the gap in time between William's rescue and his inhuman-self arriving at the Forge where Host-Emily awaits.

For more on the "Westworld" season two finale, follow all of INSIDER's coverage here.

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