"I know what happens, and it's quite moving and quite beautiful," he told Variety Friday.
But — surprise, surprise — he's not saying much more than that. "I will hold this one to my grave, I promise," he said. "This is a big one."
Harbour, who's known how the hit series concludes for some time now, pried the details out of creators Matt and Ross Duffer by being persistent.
Netflix David Harbour as Jim Hopper in 'Stranger Things'
"I think it varies from person to person, from character to character, and I'm such a harassment specialist that I think I've gotten it out of them," he said. "It's been back and forth about like, 'What happens to Hopper? Is he a character that's able to survive Hawkins or does he die?'"
The Black Widow star and Tide spokesman explained why it was important for him to know where his character ends up and why he ends up there. "I had to know that going in so I knew where to arc it," he said. "I think there's a responsibility in terms of how Hopper ends up that I'm eager for people to see."
Harbour previously revealed that he had the skinny in 2021, telling MTV's Joshua Horowitz, "It's cool for me. It sucks for you."
He also told Horowitz that Netflix sent frequent emails reminding the cast not to disclose anything about the show, including when they're in production.
Despite this, Harbour discussed some details about season 4 in his Variety interview — namely, that he filmed most of the season away from the bulk of the cast. His ST character, Jim Hopper, appeared to have died at the end of season 3, and much of his scenes in the upcoming season were shot in Lithuania, serving as a stand-in for a Russian prison.
"To have him be so far away with a bunch of Lithuanians who didn't speak English was kind of fun," Harbour says. "It was like doing a big old prison escape movie on my own."
At last year's New York Comic Con, Harbour compared his season 4 storyline with From Russia With Love, The Great Escape, and Alien 3.
"I think I have the best storyline," he said. "And then you'll see a lot more layers about Eleven [Millie Bobby Brown] and Brenner [Matthew Modine] and the institution and what she went through and is going through that relates to this narrative coming back."
Harbour also told Variety that he welcomed the opportunity to play a Hopper who's been stripped bare and pared down to the core of who he really is. "I was like, 'We've got fat dad Hopper pretty much in the can. We may as well try something new,'" he said.
Netflix will release the first half of Stranger Things season 4 on May 27, with the last two supersized episodes dropping July 1. The show will then wrap things up with a fifth and final season.
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