John Green had major doubts that his 2017 novel, Turtles All the Way Down, could work as a movie. It takes place inside the mind of a teenage girl named Aza with severe OCD, inspired by Green’s own experiences with the illness. “It’s so deeply enmeshed in this one girl’s brain that the plot basically keeps getting interrupted by her brain!” Green says cheerfully over Zoom. “I thought that posed a huge challenge to a filmmaker.” He was first approached about optioning it the day the book came out. After all, it was his first since his best-selling novel The Fault in Our Stars, which was also adapted into a hit movie. But Green was deeply reluctant to move forward with the project—until he met Hannah Marks.

Marks was just 23 when she first pitched her ideas for a Turtles All the Way Down movie. A former child actor, she would go on to direct the movies After Everything and Don’t Make Me Go. But at the time, she mostly won over Green and the producers with her vision for Turtles. “She’d put together this two-minute video that captured how she wanted to portray [Aza’s] thought spirals,” Green recalls. “It made me feel the thing. That’s how I feel about the movie too. She found a way to capture the richness and fullness of this person’s life and their relationships, but at the same time how the illness pulls you out of that, and makes every aspect of that so challenging. She really had a visual language for it from the very beginning.”

A huge John Green fan, Marks (now 31) was stunned when she got the gig. “It was crazy. I was like, Are you guys sure?” She had no idea that it would take seven years for the project—originally intended as a theatrical film—to make it to Max, where it will premiere May 2. But her strong feelings about the book kept her going. “I had never read something that felt so honest and raw about OCD or anxiety,” she says. “I have very similar issues to Aza, so I connected with her deeply.”

Turtles is a coming-of-age tale with romance, mystery, and female friendship woven through it. But OCD pulses at its core, and it was essential to nail that element. Marks and Green were both aware of the way OCD had sometimes been portrayed onscreen, as either a quirky superpower or freakish behavior. “My experience of OCD is that you’ll do whatever you need to do to make the obsessive thought spiral stop, because it’s extremely painful,” Green says. “And so the compulsive behaviors are not freakish—they make a lot of internal sense when you’re trying to confront intense pain.” Once Isabela Merced was cast as Aza, he felt convinced that she could bring a sense of richness to her world.

Green was on set most days, and Marks says she consulted with him regularly on everything from the size of the callus Aza compulsively picks at to the dialogue for her thought spirals. Marks says she had done a lot of advance emotional preparation for tougher scenes so she could come to set and be professional. “But I know that was definitely tough on John,” she says, “coming in and seeing something he wrote come to life.” Green says the worst part was watching Merced have to enact things that he experiences as torture. “I worried about her, and there were a couple times when I wanted to stop,” he recalls. “But she would reassure me that she was okay.”

One scene, in which Aza’s best friend, Daisy (played by the effervescent, mononymous Cree), accuses her of being self-centered and best taken in small doses, especially resonates for Green. “I’ve had conversations with my closest friends where they said versions of it over the years, mostly when I was a lot younger,” he says. “I know what they mean, and yet it’s really hurtful. That’s something I thought about a lot in my own life. You know that line on Tiktok, ‘Is it me? Am I the drama?’” But Green makes clear that he doesn’t see Aza as a bad friend. “I think she’s ill. That’s why it’s really important that the story doesn’t end there.”

Screenwriters Elizabeth Berger and Isaac Aptaker changed elements of the book to externalize the action, creating a whole new professor character (J. Smith-Cameron) whose online lectures on free will provide inspiration for Aza. “That’s ultimately Aza’s question: Am I making these choices, or are these choices making me?” Green says. “One of the things that I really love about working with Hannah is that she took those questions really seriously, and explored them visually.”

Marks says that she fought to stay faithful to the book and drop in every Easter egg possible, “whereas John was actually less precious than I was. So I was really approaching it as this as a fangirl of his, like, we have to include every detail! And he felt like, no, it’s okay, we’re making a movie.”

One thing was not negotiable: Marks was determined to include a cameo of Green. His appearances had been cut from previous adaptations of his books because, he says with a grin, “I'm such a bad actor! Distractingly bad.” Although there was some talk of making him Aza and Daisy’s boss at the Chuck E. Cheese–style kids’ game center they work at, he eventually was cast as a gym teacher.

“I used it as an opportunity to troll him,” Marks says gleefully. “He got more takes than anybody in the movie, and I kept making him do squats and just absolutely ridiculous things to test his trust for me.” When it came time for his bit of dialogue, though, Green panicked. “I’m just frozen, absolutely frozen. I have no idea what’s happening. And after, like, 30 seconds, I finally say, ‘Line?’ because I’ve forgotten my one line.”

Marks also gave herself a small role, playing a waiter who regularly serves the girls. “She’s an exhausted waitress in John’s book, so I thought that was the one place I really could commit myself, because I was already exhausted,” the director says with a smile. As an actor, she’s appeared in dozens of movies and shows, including Criminal Minds, The Runaways, The Amazing Spider-Man, Dirk Gently’s Holistic Detective Agency, and Weeds. On the latter, her character engaged in some pretty adult behavior—which may be why Marks’s mother originally turned down the part for her 13- or 14-year-old daughter. “I called my manager behind her back and said, ‘I’m going to do it anyways,’” she admits. “I didn’t even understand a lot of my more sexual dialogue at the time.”

Although she’s interested in the conversation over child actors that has recently re-erupted thanks to the docuseries Quiet on Set, Marks says she had to stop watching that series five minutes in. “I just don’t think I can go there,” she says. “I definitely look back on experiences that I had growing up in this business, and I know things would be different today. I don’t think I was even aware that HR existed.” She hates that anyone can easily google pictures of her going through puberty, but she also sees an upside to her youthful experience. “The fact that I started so young is probably why I’m able to be here right now and be a director. Being on sets was such a big part of my childhood; I got to learn a lot really fast, at that age when you’re such a sponge.”

Marks began considering a career as a screenwriter and director in her teens. “I was always a working child actor, but I was never famous, so I found myself getting kind of bitter and jaded at a young age. And I didn’t want to be ” she says. “Some of the people that played my mom on shows, I felt like they weren’t happy, and I saw that as my future.” Marks currently has multiple projects on the go, including Razzlekhan, a movie she’s writing and directing based on the true story of a “bonkers” cryptocurrency heist. She’s excited to be working on a story about people in their 20s and 30s. “I want to grow with my characters,” she says, “and not get pigeonholed into only telling teenage girls stories, even though I love them.”

As for Green, he’s been consumed by nonfiction since Turtles All the Way Down. In 2021 he published The Anthropocene Reviewed: Essays on a Human-Centered Planet. More recently he’s become a tuberculosis advocate, with his family pledging millions toward funding to test and treat the disease. After immersing himself in research, he says he has written a book about TB that will come out next year. “My editor has it right now,” Green says. “It’s half about historical human responses to this deadliest infection we’ve ever had, and half about one contemporary kid’s challenge of navigating the TB care system in the 21st century.”

What will he do after that? “I think I’ll return to writing novels,” he says hesitantly. “Maybe. I hope? I’m trying.”

I ask Green about a comment he’d made on X about a photo of him surrounded by Marks and the cast of Turtles. “I love this picture because it looks like the poster for a sitcom about four cool young people and their weird dad,” he wrote. Does it feel awkward writing about young people as he gets ever older?

After pointing out that he never really felt like a teenager even when he was one (“I always felt like I was observing them from a distance, almost anthropologically”), Green answers by way of story about his struggle to find an ending for Turtles All the Way Down. Alone in a cabin, he called his wife for help. She suggested he flash-forward to Aza’s future. “There’s one thing that you classically don’t do in a YA novel, which is to have a time jump, because it’s like looking back on adolescence, not in it,” Green explains. Gripped by desperation, he decided to break the rules and try it.

“Maybe that’s you acknowledging that there’s this distance between you and the reader now, or even that there’s this distance between you and the self you were when you wrote Looking for Alaska or The Fault in Our Stars,” he thought to himself. “Once I did the time jump, I realized I could be kind to that character in a way that she couldn’t be kind to herself in the moment.” It was also a note to self: “I was going back and saying to myself: You’re so sick, and I’m so sorry, more than anything. I’m so sorry, and you’re going to get through this.” I try to covertly wipe my moist eyes as one of the world’s most beloved YA authors continues. “I remember thinking as I was writing that, like, Does that mean this is it? And maybe it did.”