The screenwriters of Netflix's 'Spiderhead' talk spoilers, the original ending, and coming up with that yacht-rock soundtrack

Shortly after Saunders' short "Escape From Spiderhead" was published in The New Yorker, Reese and Wernick found it in their hands with the hopes that they could adapt it into a movie.

Both were instantly intrigued, but there was an obstacle: it's a very short story. At only around 7,700 words, it was sparse for movie adaptation standards.

"It's brilliant, but it doesn't have a beginning, middle, and end," Wernick said.

As a result, the screenwriters had to greatly expand on what Saunders was trying to get across in the story. And that's where things got tricky.

"You're trying to mimic the author's voice and it's not always the easiest thing in the world, a writer to mimic another's voice," Reese said. "That was our biggest fear and our biggest challenge and I think readers of the short story and watchers of the movie will compare them and they will make their own determination whether we were able to capture it or not."

So to get on the right foot, the screenwriters said they used almost every piece of dialogue Saunders wrote and put it into the script.

But then came the next challenge: the short's grim ending.

The short ends with Jeff killing himself in the Spiderhead. Reese and Wernick said they wanted to go in a different direction.

"We thought in a feature film we couldn't have the protagonist kill himself," Wernick said. "It would just be too much of a downer. So we ultimately had to dive in and reverse engineer how it ends and make it feel more redemptive for Jeff."

The ending was changed to Jeff and fellow inmate Lizzy (Jurnee Smollett) escaping the Spiderhead facility after being freed from the "pack" of drugs that are attached to them.

Another change from the book's ending is that Hemsworth's character, Steve, dies.

Hooked on the drugs he'd been giving the inmates, at the end of the movie, Steve's pack malfunctions. So while trying to make his own escape, as authorities are on their way, he flies into a mountain as he experiences pure ecstasy from his own drug.

But that wasn't Steve's original fate. That changed during the writing phase thanks to a suggestion from "Spiderhead" author George Saunders.

With Jeff escaping the Spiderhead, Reese and Wernick turned their attention toward its evil mastermind, determining that Steve should be the one to perish.

And originally Hemsworth's character had a much uglier sendoff.

In one of the earlier drafts, Reese and Wernick had Jeff get all the inmates into the Spiderhead where they then kill Steve.

"They were going to revenge themselves on Steve," Reese said. "They ended up tearing him apart."

However, Reese said, when they gave that version of the script to Saunders for his feedback, he wasn't into that storyline. He felt it was the wrong move for Jeff, who needed to redeem himself.

"It can't be directly Jeff making an active decision to kill Steve because then Jeff hasn't learned much," Reese recalled of Saunders' feedback. "And that just hit us like a ton of bricks, he was absolutely right."

From there, they pivoted to the ending we see in the final cut.

"The fact that he had these drugs into his system and he's experiencing all these different emotions when he can least afford to experience them — he's flying his plane and that's how he dies — we felt that was pretty juicy," Reese said.

"And George loved that," he added.

Reese and Wernick said that one of the biggest joys of the project was watching Hemsworth showing his range as an actor.

"It was nice to see him expand beyond what we're used to seeing him in," Wernick said.

They said the key was that Hemsworth brought a likability to the character.

"He did the difficult thing of the likably unlikable character," Reese said. "A character that is unlikeable but you can't help to be seduced by him a little bit and be entertained and even like him even though you know what he's doing is bad. He rode that razor's edge beautifully."

And Wernick said their model for the character was one of the greatest minds in the world who also wasn't always likable.

"When we were crafting the character, Steve Jobs was our north star," Wernick said. "The idea that in Steve Abnesti's own mind, he's not a villain. He thinks he's changing the world."

"But what Jeff and the audience realizes is these are human beings and he's treating them like lab rats and ultimately what he's doing is wrong," he continued. "But up until the very last minute, Steve is not the villain in his own mind."

In a trippy movie about overpowering drugs, you need some off-the-wall needle drops. And right from the opening credits, you get that.

"Spiderhead" is filled with smooth '70s rock songs that are best categorized these days as "yacht rock."

From Michael McDonald to Hall & Oates, the music contributes a numbness to the madness happening on-screen. Reese and Wernick said the idea was also to make it so the inmates were hearing the same music.

"The music wasn't originally written into the script," Reese said. "We were rewriting the script and we were in a conversation with Joe Kosinski and Eric Newman, our producer, and Chris Hemsworth might have even been in on the meeting, and we wanted the music to be something that was playing, not just for the audience, but also for the inmates within the scenes."

"So we thought it really had to come from character, what does Steve listen to? Or what does he force his inmates to listen to?" Reese continued.

It was in that meeting that the idea for a yacht-rock soundtrack came up.

"We felt Steve has this funny sense of humor and that he legitimately would love yacht rock and force everybody to listen to it. Almost like hell's playlist," Reese said. "So then we started the fun search for songs."

Reese said he insisted on having the Poco song "Crazy Love" be what plays at the end during Jeff and Lizzy's escape as well as Steve's death.

The screenwriters said there was a large budget for music clearances and every penny was needed — especially for the Supertramp classic, "The Logical Song," which opens the movie.

"That one is super expensive as it turns out," Reese said.