Emma Stone and Jonah Hill in a totally not-weird scene from Maniac. Photo: Michele K. Short / Netflix

Maniac is an experimental show about an experiment in curing mental illness. It is wild, audacious, addictive, and teeters so precariously between reality and fantasy that the audience will immediately question what’s real and what isn’t. The bold ten-episode series, one of the fall season’s best, repeatedly bounces in and out of its characters’ brains and hop-skips from genre to genre, yet somehow avoids spiraling out of control even when what transpires detours further into WTF-ville.

The unconventional narrative follows two New Yorkers, Annie Landsberg (Emma Stone) and Owen Milgram (Jonah Hill), who volunteer to participate in a pharmaceutical trial that purports to permanently cure them of all mental-health problems. During the study, a series of drugs push them to explore various corners of their subconscious while exhuming traumas they have tried their best to bury. By signing up to star in Maniac, Stone and Hill not only get to depict that clinical journey, they also assume a diverse array of personas that Annie and Owen take on in their minds once the drugs take effect. Among other things, Maniac features Stone as a kinda-sorta Legolas in a knockoff of Lord of the Rings, Hill as an Austrian government underling with an Austrian-Finnish-Swedish-Dutch-Italian-Icelandic accent, and both as a married Long Island couple in the 1980s who get involved in a Coen brothers–esque caper involving a stolen lemur named Wendy.

If that sounds weird, please know that I have only scratched the surface of this particular synapse. Maniac also gives us a panicky Justin Theroux in an awful toupee, Billy Magnussen as a douche of many different colors, and Sally Field in a dual — or is it triple? — role that slyly tips its hat to her Emmy-winning performance in the mini-series Sybil. You know how sometimes in life you don’t realize how much you needed something until it appears? That is how I feel about the moment in Maniac when a fired-up Field confidently throws her hands behind her head and says, “Gas up the Miata.”

The ringleaders of this psychological circus are creator and co-writer Patrick Somerville, who worked on The Leftovers, and Cary Joji Fukunaga, the True Detective season-one auteur who directs every episode of Maniac with understated but unmistakable verve. The fact that Somerville is responsible for this dramedy, based very loosely on a Norwegian series of the same name, makes sense. The pitch for Maniac could very easily have been “Let’s make a series where nearly every episode is like the ‘International Assassin’ one from The Leftovers.” (Nick Cuse, who co-wrote that episode of The Leftovers, is also a writer and co-producer of Maniac.) But Maniac is more than an exercise in switcheroos of form and tone. It also considers the psychological barriers that prevent human beings from shedding their baggage, and the factors that bond two people to each other. Because of its surprises and its interest in the relationship dynamic between Annie and Owen, Maniac could easily serve as a binge-watch companion piece to another of this season’s streaming TV delights, Amazon’s Forever.

The first episode zeroes in on Owen, while the second is told from Annie’s point of view, but both focus on what happens as they prepare to walk through the doors of Neberdine Pharmaceutical to engage in that three-day drug trial. Owen is a newly unemployed schizophrenic who spent time in a mental hospital because of his tendency to hear voices and see things that aren’t there. He’s one of several siblings, including golden boy Jed (Magnussen), in a very wealthy family that passive-aggressively ostracizes Owen. In one of the show’s many droll visual moments, the camera reveals a massive, pretentious painting of every member of the Milgram family that hangs on the wall of their home, then pans a few inches to the right, where a tiny framed picture of Owen hangs all by itself. When Owen arrives at Neberdine and sees Annie, his delusions convince him that she has been preordained to partner with him and save the world.

Annie may have a firmer grip on reality, but she is untethered in her own ways, consumed by guilt over the rupture of her relationship with her sister Ellie (Julia Garner, who, between this and Ozark, is quickly becoming a Netflix MVP). Annie is eager to down those meds in the hope that they will finally relieve her of the guilt and sadness she’s carrying. She is also dismissive of Owen at first, but after they disappear into the first of several medically monitored dream states, she finds reason to believe that perhaps the two of them have potential as a dynamic duo after all.

Every time Owen and Annie are under the influence, the people and issues they encountered in real life rear their heads in increasingly warped and fantastical contexts, like that previously mentioned lemur caper, or a seance at a secluded mansion circa 1947. Each episode unfolds at a concise (for Netflix) pace of 45 minutes or less, which keeps Maniac zipping along with the speed of an electrical impulse rocketing from neuron to neuron.

Maniac doesn’t unfold in a consistently defined setting, particularly with regard to the time in which it takes place. Though its present-day scenes unfold in New York, it’s a version of New York that’s either in a cockeyed future or an alternate version of right now. For example, practically everything runs on computers, but the computers look about as advanced as the ones in the movie WarGames. Instead of the Statue of Liberty as we know it, New York Harbor is occupied by what a tour guide calls “the Statue of Extra Liberty.” These kinds of paradoxical details are part of what makes the world of this series so fascinating. So does the superb production design by Alex DiGerlando (Beasts of the Southern Wild, True Detective) who infuses the Neberdine lab with classic sci-fi details, from the spare, white, Kubrickian subjects’ living area to the massive sensors that monitor patients’ brain waves and make them look like robots from a long-forgotten ’50s outer-space flick.

It’s also fun to watch the cast take some off-kilter risks. As Dr. James K. Mantleray, who assumes control of the pharma study three episodes in, Theroux ditches any semblance of heroics to morph into a nebbish in a pair of oversize glasses — the costumes by Jenny Eagan are terrific — and he radiates a sense of anxiety that only heightens when his mother, Greta Mantleray (Field) enters the picture. The hypercompulsive way that Theroux slathers on lip balm just before reuniting with his mom says everything you need to know about how freaky and dysfunctional that relationship is.

Field is … well, she’s the great Sally Field. She’s as grounded as Greta Mantleray, a pop therapist diva whose best-selling titles include I’m Okay, You’re a Bitch, as she is when playing the personification of the lab’s supercomputer, GRTA, at its most emotionally fragile. (Yes, one of the roles Field plays is a computer.) Sonoya Mizuno, whose oversize spectacles mirror the ones worn by James, also stands out as Mantleray’s Neberdine colleague, Dr. Fujita. Repressed, fixated on the study, and constantly smoking, she’s a compulsive tic in human form.

Ultimately, though, Maniac belongs to Stone and Hill, who are repeatedly offered invitations to gnaw the hell out of all the meticulously designed scenery around them and resist it every time. Hill’s Owen is mired enough in his condition that he often speaks in a monotone, but when he becomes other versions of himself during treatment, he shows loving, menacing, or totally goofy sides. Stone has no trouble at all dancing between the heartbreak of Annie’s confrontations with Ellie, the ludicrousness of becoming an elf in a pseudo-Shire embedded in her subconscious (“Fantasy is my least favorite genre,” Annie complains), or a sexy assassin with a southern accent who knows her way around a firearm.

Stone turns into that kill machine in the ninth episode, a real banger, complete with a Dr. Strangelove–esque scene that provides a showcase for Hill at his most absurd and a knockout gun battle that unfolds in one take, a reminder of that famous extended True Detective shot that established Fukunaga’s bona fides as a director.

Maniac is exhilarating to watch and a lot to process. It’s not as interested in highlighting the realities of depression or other mental illnesses as it is in capturing the core truths about them: how they isolate people, play tricks inside the brain, and can’t necessarily be cured through any single, simple means. It’s most accurate to describe it as a drama, but it’s really a hybrid of a bunch of genres, including dark comedy. The fact that it’s so consistently able to elicit laughter is one of Maniac’s best qualities. That, and its full embrace of utter randomness. Did I mention that at one point, Jonah Hill turns into a hawk on this show? Because if I didn’t, it’s worth noting.

“No one sees into your heads but us,” James promises his subjects before the study gets underway. But that’s not true. Maniac lets us see right into Annie’s and Owen’s synced-up, askew minds. Once we start peeping around in there, it’s next to impossible to look away.