Rian Johnson’s journey to creating the Knives Out cinematic universe — which expands on Dec. 23, when Glass Onion: A Knives Out Mystery premieres on Netflix — all started with Agatha Christie. “I am a whodunit junkie,” the director tells Krista Smith in a new episode of the podcast Skip Intro, adding: “When I was a kid, there were always Agatha Christie paperbacks on the shelf at my parents’ home. It felt like the first adult book that I would pick off the shelf as a kid and start reading.”

Johnson says he was drawn to the humor of Hercule Poirot, Christie’s famous detective who appears in more than 30 of her novels, and also to the sociopolitical undercurrents that the author wove into her mysteries. “When Christie was writing those, she wasn’t writing these quaint little things set in the past. She wasn’t writing little nostalgic things. She wasn’t writing things that were contained and out of our world. She was writing to her time, and she was writing in the moment and she was engaging with her current culture.”

Inspired by Christie, Johnson set out to tell a story that reflected his own time, wrapped up in the trappings of the genre he loves. “Let’s write a whodunit that takes place in America right now, and let’s engage with what's happening right now,” he remembers thinking. “Not that these are huge social messages or huge political or culture or movies, whatever. They’re largely whodunits, and they’re mostly entertainments, but just like Christie did, they’re also engaged with [the world]. In this case, [America in] the 2020s.”

As every whodunit enthusiast knows, you need an engaging detective to lead the charge. And that’s where Johnson hit his first roadblock. “When I started writing the Benoit Blanc character, I think I screwed myself up because I started [thinking], ‘I have to create a Poirot. I have to create a Sherlock. I need quirks,’” he says. “And so I started loading him up with all these quirks and he just became ridiculous. It was like, ‘What if he had a monocle? What if you had an eye patch? What if he had different-colored eyes?’ And finally, I said, ‘OK, you know what? I’m not going to try and create a character on the page beyond what his actions are in the mystery.’”

In the end, it was Daniel Craig who, armed only with what Johnson called “a light Southern drawl,” built up Benoit Blanc’s supersleuth persona. “It wasn’t like we changed the dialogue or changed the script or anything, but just Daniel inhabiting that role and bringing his vibe to it instantly brought it to life,” Johnson says. “ And no eye patch required, thank god.”

So what’s next? With Glass Onion about to premiere on Netflix on Dec. 23, Johnson says he’s ready to think about the next mystery. “I’m already starting to, not because I feel like, ‘Boy, I better get the next one going,’ but because it’s so much fun,” he says. “The other thing that gets me genuinely excited is Knives Out and Glass Onion are so different, and that’s something that harkens back to Christie in another way. How she would always find ways of completely shaking it up from book to book and making it exciting for the reader. She was creatively challenging herself each time.”

Likewise, Johnson wants each of his films to have its own personality. Be ready for the third installment of the Knives Out franchise to stand out, he says. “Beyond setting, beyond bikinis versus sweaters, it truly is going to be trying something different narratively and tonally. I’m already excited about doing the next one.”

Glass Onion is now playing in theaters for a limited one-week engagement before it premieres on Netflix Dec. 23. For more behind-the-scenes insights, tune in to this week’s Skip Intro on Apple, Spotify or wherever you get your podcasts.