In Bong Joon Ho’s world, everyone is a parasite, of sorts, to someone else. At the top is the Park family, with its patriarch working in the lucrative tech industry, presumably in VR as he is seen asking questions about an Oculus-like device. In a lesser story, he’d be cold and detached; a ruthless businessman with no time for his family. But Dong-ik (Sun-kyun Lee) is lovingly intimate with his wife Yeon-kyo (Yeo-jeong), who he views as a partner, kids around with his daughter Da-hye (Jung Ji-so) and dotes on his ADHD artiste-in-training son Da-song (Hyun-jun Jung).

They are warm and caring. They could be the protagonists.

On the other side of town lives the Kim family. Like the Parks, they are a warm family unit. The only thing separating them is their social station. The Kim family is comprised of the father Ki-taek (Kang-ho Song), his wife Chung-sook (Hye-jin Jang) and their two kids Ki-woo (Woo-sik Choi) and Ki-jung (So-dam Park). In a brisk, economic bit of storytelling, Bong Joon Ho quickly establishes how poor their family is. Their phones have been shut off and the cafe they’ve been siphoning free Wi-Fi from has just changed its password. They barely get by, doing odd jobs like folding pizza boxes and keeping in touch with the outside world through WhattsApp.

That night, we learn of the third level of parasites in the world Bong has created, as Ki-taek flicks a stink bug off the table with callous disregard; no matter your station in life, there’s someone or something worse off. And when the city exterminator comes by, spraying pesticides through the streets, Ki-taek tells his family to leave the windows open. It’s free extermination after all, he reasons, as they cough while inhaling the toxic fumes.

The Kim family has been forced to become grifters, grabbing a meal and a deal wherever they can. So when the opportunity arises for Ki-woo to tutor Da-hye, of the fabulously rich Park family, he immediately jumps at the opportunity. As Ki-woo inserts himself in the Park family, he sees them as overwhelmingly nice and warm, if a bit odd. Da-hye has an instant attraction to Ki-woo, who the family has decided should be called “Kevin.” Da-hye’s brother, meanwhile, is an “American Indian”-obsessed painter whose self-portraits Ki-woo mistakes for a chimpanzee.

“It’s so metaphorical,” Ki-woo muses.

Yeon-kyo wants to nurture her son’s dubious talents and wouldn’t you know it, Ki-woo knows just the person: a professional art therapist. That “professional” is, of course, his artistic sister, who has developed her own backstory about being Jessica from Chicago. And so it goes, with the Kim family slowly wedging themselves into the Park family, like the bugs that wormed their way into the Kim household.

Bong Joon Ho uses set design to further examine his characters. The Kim family live in a home that’s one step away from being subterranean. Their only view to the outside world is a basement window, sitting at foot level. Their home is cluttered; socks hanging from the ceiling to dry and dishes and papers amassing wherever there’s a free place.

Meanwhile, the Park house, built by a famed architect, is full of sharp angles, modern design and coldly beautiful sterility. The living room is framed by a wall-to-wall window, showing the beautiful trees and nature just outside their home. It’s a stark contrast to how the Kim family is forced to live and digs into one of the themes Parasite examines. “Money is an iron. It smooths out all the creases,” Chung-sook says dismissively of the rich. And the two households immediately showcases that statement, as the Park household is glisteningly clean and uncluttered, the creases ironed out to perfection. In comparison, The Kim household is nothing but one large crease.

It’s the little things like this that makes it obvious Bong Joon Ho is firing on all cylinders in Parasite. Here’s a director operating at the top of his game and the results are magnificent. From the first scene, I knew I was in the hands of a master, as he managed to elicit laughs one minute and uncomfortable, squirmy silence just moments later. As expected, Parasite glides between genres—sometimes in the same scene—with gleeful abandon. What starts as a hilarious story about a family of grifters swindling the clueless rich starts to insidiously change tone.

When it slowly unveils its hand, Bong masterfully manipulates the tension like a rubber band, continually pulling it to the point the audience is just waiting for that painful snap. But it’s the playful way he manages to make the audience laugh before blindsiding them with some of the twists and turns proves that Parasite is easily his most assured and thematically rich work. And in such a fantastic oeuvre as his, that’s saying something.

It’d be easy to suggest that the narrative is about the oppression of the poor and the clueless callousness of the rich. And, sure, that’s part of it. But Bong Joon ho doesn’t paint with broad strokes. The Park family isn’t full of Machiavellian schemers. One of my favorite scenes is Mr. and Mrs. Park deciding to sleep on the couch so they can watch their son sleep outside in the yard.

They nurture his dubious talents and help set their daughter up to succeed in school through tutors. Obviously their wealth affords them immense privilege to be able to do this. And the script doesn’t let them off the hook. They have a mean streak, like how dismissive Mr. Park is about the way his servants smell—like turnips or boiled rags. But they aren’t the mustache-twirling villains you’d typically see in this type of movie.

In a way, they are more insidious.

Going back to the stink bug comparison, in the same way Ki-taek can casually flick bug off his table, the Park family could just as easily squash the Kim family’s future. It’s all a matter of perspective in Parasite. And while the Kim family exhibits some of the traits of literal parasites, digging into the Park family and suckling at their wealth, Bong manages to subvert expectations about what a parasite actually is. Ultimately, it’s the Parks who seem like the real parasites of society, enjoying their success and wealth, built on the backs of the people who are literally drowning while they can blissfully appreciate the rain.

Parasite is a mature and complex examination of the cyclical nature of the haves and have-notes. It’s probably the best film I’ve seen this year.