Despite being killed off at the end of Season 4, Papa will return for the show’s final installment. What does it mean?

Matthew Modine as Dr. Martin Brenner in Stranger Things

In the fourth season of Stranger Things, Dr. Martin Brenner a.k.a. Papa (Matthew Modine) was killed by the military, who’d been sent to his lab to capture Eleven under the false belief that she was murdering the teens of Hawkins. It was a fairly emotional goodbye, with Brenner pleading for Eleven to understand why he did what he did to her, and Eleven rightfully refusing to give him that absolution.

But as Modine teased on Instagram, it wasn’t the end of his character’s arc on the show after all. In the short behind-the-scenes video, which he appropriately hashtagged “indestructible,” he’s seen getting aged up for Season 5, suggesting that Brenner won’t merely appear in flashback for the series’ final run, either.

So what happens to Brenner in Season 5? “I think if I told you any of that, Netflix would get me and tie me up by my big toes and hang me out on the street,” Modine told Parade in an interview to mark the 40th anniversary of his 1985 cult classic Vision Quest.

But the Full Metal Jacket actor did offer a rather telling tease for Brenner’s return nonetheless: “I think the fascinating thing about Dr. Brenner is: How did he get that job?” Modine said. “How do you go to the government and say, ‘I want to do these experiments with young children and teach them psychic powers?’”

“You’d have to be qualified for that job,” he continued. “So I think that the interesting thing about Dr. Brenner is that he might be patient number zero. You know, that he might be his own—he might be the most powerful person in the room of those children with those psychic powers. I’m going to leave it right there.”

Vecna is patient 001, which does seem to imply that there’s a patient zero. Plus, the theory might explain how Brenner survived being mauled by a Demogorgon at the end of Season 1. But fans will have to wait to find out for sure how and why Brenner comes back.

The fifth and final season of Stranger Things is due out later this year on Netflix.