David Harbour says he has not heard from the creators, The Duffer Brothers, about reprising Chief Jim Hopper in "Stranger Things" Season 4, and that they have kept the identity of the American a secret to him.

A popular fan theory is that Hopper is the American taken captive by the Russian soldiers in the end-credits scene of Season 3. Viewers believe that he is still alive after he survived the explosion at Star Court mall, where he is presumed to have died.

Fans claimed that he somehow escaped in the few seconds when Joyce turned to look away when she activated the explosion. They believe that he is alive because his corpse was never found on the scene. Some suggested he escaped through the crack in the wall that leads to The Upside Down, which could have landed him in a Russian prison.

However, Harbour admitted that he has grown less certain that Hopper is the American because he has not heard back from The Duffer Brothers about returning to "Stranger Things" Season 4. He also revealed that he read about the American months before they filmed Season 3 Episode 8. At the time, he was sure that he is the prisoner but the creators never confirmed this with him.

"I remember reading that episode, and they hadn't told me this whole thing about this Russian facility at the end and how that was gonna be the sort of teaser and like 'The American' and the Demogorgon," Harbour told The Wrap.

"They hadn't told me about any of that, actually, and I just read it in the script and I thought it was amazing. And I really thought I was 'The American,' and then I haven't heard a lot from them. So I really don't know if I am. But I thought I was, but it was never discussed," he added with a laugh.

Harbour said he did not ask the showrunners about the identity of the American because he was confident that it was Hopper. But now, he admits that he is not so confident anymore.

Regardless, Harbour shared that he is keeping his schedule open in case Hopper is indeed the captive American. He admitted that he wants to see Hopper alive in "Stranger Things" Season 4.

David Harbour in Stranger Things
David Harbour plays Chief Jim Hopper in "Stranger Things." Netflix / YouTube