Warning: mild spoilers below for the first five episodes of Westworld season 2, including the promotional teaser for episode 6.

For most of the people watching HBO’s science fiction series Westworld, when Betty Gabriel’s character Maling mentions “the Cradle” in the second season’s third episode, it’s just a throwaway reference. But hardcore fans know better — at least, the ones who have been willing to dive into the in-world websites, chatbots, and email blasts that serve as the show’s viral marketing campaign. They know the Cradle is a simulation technology, and Delos, Inc. uses it to test storylines before they’re deployed in the company’s parks. In-the-know fans are aware of the Cradle’s codename (CR4-DL) and have seen schematics of the system, which made a quiet appearance in a trailer all the way back in March.

It makes sense that Westworld, a show about a digital re-creation of the real world, is using an online extension of its fictional world to expand its narrative landscape. In the process, the creators are offering backstory and insights that can’t be found anywhere else, so the biggest fans can discover some of the show’s deepest secrets before they make it to air.

Upping the ante

HBO’s promotional strategy this year is an amped-up extension of what the network originally tested in 2016 when the show debuted. Back then, the focus was largely on a fictional website that let fans research a visit to the Westworld park, in the same way they would if they were readying a trip to Disney World. “One of my favorite quotes from season 1 is from the host Angela: ‘Figuring out how it works is half the fun,’” says Emily Giannusa, director of digital and social media at HBO. “That is something we wanted our super fans to be part of. We saw how they played along in season 1, and definitely wanted to extend that to season 2.”

The campaign for the second season kicked off in February with a Super Bowl ad, which had a secret binary code hidden in one of its frames. When translated, that code led to a website for Delos Destinations, the division that makes Westworld and its sibling parks. Since then, the campaign has unfurled a sprawling series of images, puzzles, codes, and other sites that have built out the mythology and allowed fans to dip their toes into the world of the series on a daily basis. (We’ve assembled a timeline of the campaign, and its biggest story reveals.)

Created in concert with the ‘Westworld’ writers’ room

From hosts “taking over” Westworld’s website in the same way they’ve taken over the park, to Aeden, a chatbot “host” visitors can talk with to learn about the world, the viral campaign has stayed in careful sync with the series’s storylines. That’s the result of close collaboration between Giannusa, HBO’s digital marketing team, and the production company Kilter Films, founded by Westworld creators Lisa Joy and Jonathan Nolan.

“Part of my role working at Kilter is to be the mouthpiece for the writers’ room,” explains associate producer Halle Phillips. “The communication between our marketing campaign, HBO, and the room is really close because obviously, Westworld has a complex and robust mythology. In order to do it justice, we need to know exactly where it is and where it’s going. A really important part is that [the campaign] feels like a piece of what’s happening in the show.”

Expanding the story world

Over the course of the first five episodes of season 2, that’s meant weekly updates that expand on, and even telegraph, some of the show’s narrative revelations. A mysterious mini-site tied to “The Door” — the quest Ed Harris’ Man in Black is pursuing this season — was eventually revealed to be the residence of a host clone of James Delos. When the existence of a park inspired by the British Raj was revealed, a “Discover The Raj” site popped up that night. When the show finally visited Shogun World, that park got its own new site, as well — one that copies heavily from the Discover Westworld site, echoing the idea of self-plagiarism that the season’s fifth episode plays for laughs.

Using the sites, fans can track the movement of characters like Dolores (Evan Rachel Wood) and Maeve (Thandie Newton) or get status updates on Bernard Lowe’s mental health. The promotional sites have become a viewing companion to the show’s weekly episodes, with new elements added to the sites after every airing. It’s similar to the way franchises like Star Wars use novels and comic books to build out additional details beyond what happens in the films — except the Westworld supplementary material is coming out on a weekly basis, so fans can watch an episode, then dive deep into the sites to search for additional hidden details.

“Westworld the show takes place in this very complicated theme park,” Phillips explains. “We don’t really want to spend the exposition explaining exactly how this park works.” These tie-ins let creators delve into Delos’ inner workings and enhance the audience’s understanding of the universe. The supplementary sites aren’t required reading; a Westworld fan who just wants to watch the TV show will be fine. But the approach does let fans choose their own engagement level, and it gives the most detail-driven viewers a sandbox they can explore to find answers to some of their own granular questions.

“For example, season 1,” Phillips says. “Once the hosts get shot, how do they get back into the Mesa to get repaired, and how do they get back up without anyone noticing? Well, if you’re playing in the employee intranet, they have departmental guides. The livestock department has this flowchart that explains exactly how that works.”

The hidden binary codes and in-narrative websites are intentionally designed to appeal to hardcore fans. That could pose problems, given that the campaign is trying to cater to the show’s more mainstream audience as well. “In the campaign leading up to season 2, we were really trying to get the fan base excited,” Phillips says, “and I think what’s been a blessing and a curse is that our fans are incredibly intelligent and perceptive. It’s been really rewarding to see them break down the season and break down the marketing. But we also don’t want to make the barrier to entry for the marketing so high that it only appeals to the four people who can crack that.”

The balance, she suggests, has involved thinking of Westworld’s hardcore fans as gatekeepers. They’re the ones with the savvy and dedication to discover the new layers of the campaign, and what they find then spreads out to the rest of the fan base through channels like Twitter and Facebook.

“The person who is willing to go there, who can find the binary code hidden within the trailer, unlocks a new level of the marketing that can appeal to everyone,” she says. “So even if you’re not the kind of person who would notice these black and white bars correlate to binary, and that once you translate that it turns into an IP [address]… once that has been cracked, it’s like, ‘Oh wow, there’s this whole Delos Destinations website that kind of built off the other parts.’ So you can engage with it as you want to. I think it’s about building tiers.”

A world of Easter eggs

Those tiers can vary wildly in difficulty and complexity. Some fans are so dedicated, they spelunk deep into the various websites to find random graphics filled with visual noise — only to take them apart and discover what appeared to be a tease of one of the season’s new parks. On the other end of the spectrum, those who sign up for email updates from Delos, Inc. also get traditional email blasts with links to the kind of behind-the-scenes interviews and videos expected of any reasonably well-marketed modern TV show.

According to HBO, the tiered strategy is working. Westworld’s second season is only at its halfway point, and the network says the show’s various websites have collectively racked up more than a million visits, besting what the promotional campaign achieved during the entirety of the first season. The digital strategy is also expanding. Along with Aeden, the primary Westworld chatbot, HBO recently launched “Tes.” A Facebook Messenger chatbot built in conjunction with Quartz Bot Studio, Tes lets fans sign up for a Westworld rewards program, asking them to answer various questions in line with the show’s larger themes about agency and free will.

But ultimately, Kilter Films and the HBO team see the marketing campaign as a form of storytelling in its own right. It’s meant as an expansion of the show’s broader story world, meaning that even the most mundane update in an email or on a site might be setting up some future revelation for the show.

“There are definitely things we are seeding in the sites that will come to play in later episodes, like in the next episode and the finale,” Phillips says. “There are definitely Easter eggs there that hint at things to come if you can read between the lines. The more you’re willing to engage with it, the more you’ll get out of it.”

All of which brings us back to the Cradle. While those following along with the sites have known about the simulator for weeks, the show itself just teased a new step into the Cradle on Sunday night in a preview for the sixth episode. Judging from the clip, Bernard himself will enter the Cradle’s world, which opens up the possibility that one of the Bernard storylines audiences have been following this season could have been a simulacrum the entire time. Reddit fans, already aware of the system’s true purpose, have been mulling over that theory for some time. So when the simulator does show up on-screen, they may end up with a better understanding of what’s actually going on than most viewers.

“There are definitely Easter eggs there that hint at things to come.”

That’s one benefit of being immersed in any property’s expanded universe. Just as it holds true for Game of Thrones fans who know the twists and turns of every novel or comic fans who are able to infer where the Marvel Cinematic Universe is heading, it’s also true of Westworld’s puzzle-solvers. And just as those franchises have expanded into new media and markets, Westworld may as well by using all this supplementary material to help launch new platforms.

“There is a very real desire to build out the narrative, the world, [the] characters, into different platforms,” Phillips says. “There’s no reason why the core story of Westworld can’t expand into all of our different devices, especially now that all those things seem to be converging a bit.” Modern viewers rarely sit down and watch television without distraction, she points out. Audiences may be watching on a laptop or tablet and texting or tweeting their reactions in real time. Expanding the narrative of the world to those platforms is an obvious evolution. “Watching television in and of itself is a passive experience, even though Westworld tries to challenge that a little bit. But engaging with the website or clicking through to a chatbot — all those things are participatory and real-time. So how can we use the benefits of those mediums to inform the stories we’re telling in the show, then also broaden and deepen them?”