It was revealed in Bong Joon Ho’s 2013 feature film “Snowpiercer” that the titular train needed children in order to carry on its mission of lapping the globe in perpetual motion. They were cogs in the machine — literal replacement parts — as the train was already wearing down after only a few years of tearing through the frozen tundra that Earth had become. It was a bleak look at humanity’s chance at survival that was further enhanced by themes of social unrest between the classes that divided the train.

When Graeme Manson took on the role of showrunner for the television adaptation of this title, he wanted to keep a similar tone to the film — “It was dark, but I also thought it was hilarious,” he tells Variety — and he wanted to deepen the discussion around the class warfare, but he wanted to ground the story in both the human bond and a scientific base, which led to exploring trauma of a slightly different kind.

“Everybody feels like they did their piece to destroy the world and lose everyone and everything they ever knew,” Manson says of the characters in his version of “Snowpiercer.” “Most of the fears that are present in the show are things like migration, detention, immigration, privilege, and then climate change is just something that hangs over the whole show, and what hangs over every character is guilt. Everybody has that trauma within themselves.”

In order to better understand each character’s individual emotional pain and therefore journey, a different character narrates each episode, Manson notes. This allows individual episodes to give “a little closer look — a sort-of internal look — at what makes that character tick.”

When Manson came to the show, the characters of Andre Layton, a Tailie played by Daveed Diggs, and Melanie Cavill (Jennifer Connolly), the voice of the train who claims to have a direct line to its maker, were already in place. The “Snowpiercer” TV series adaptation was first ordered to pilot at TNT in 2015 and to series in 2018, undergoing a showrunner swap, director changes, network moves and a complete reshoot of the pilot along the way. Melanie calling upon Layton, a former detective, to solve a crime aboard the train became both an entry-point into and a cornerstone of the pilot for Manson because it was “a way to see the train for the first time through someone’s eyes who is also seeing much of it for the first time,” he says.

As Layton is plucked from his lower-class life in the back of the 1,001-car train, he literally walks through the cars that separate his people from the upper classes.

“One of the things that I love so much about the film is, when you were charging up the train with the Tailie rebels, you’d never knew what was going to be on the next door. It’s just a series of doors into these strange rooms and strange encounters,” says Manson. “We really wanted to have that television show too, and I think that gives it a big cinematic feel. When we run five seasons, you can still open doors on surprising new cars.”

But Manson admits that while Layton’s investigation served as a way to set up this complicated new world, “there was never really a season-long murder mystery here. It was a way to get him out into the train. He has his own agenda, and that is one of resistance and revolution, and that’s the real story of the first season. We used the familiar to get into deeper territory.”

Layton’s travels within the train provide crucial information for him on how the train operates and the other passengers live. As Layton gets to know some of the first and second class passengers, the staff that serve them and Melanie herself, he, and the audience by extension, begins to “understand their fears and what drives them.” But more importantly, he begins to assess who can be used and who can be allies in the Tailies’ mission for a revolution to bring forth a better life.

“The revolution will be threatened,” Manson previews. “Conspiracy and secrets play heavily on the train, and misinformation, but what they are looking for is equal calories, fair representation. They’re attempting to write a constitution and we all know what that is. They’re attempting to revive democracy, and especially in these times, I think that is something important. It’s another one of those [areas] where the show rubs up against our current reality.”

“Snowpiercer” premieres May 17 on TNT.