One of the biggest surprises of Star Wars: The Force Awakens was just how little of Mark Hamill’s Luke Skywalker was in the film. Luke’s presence loomed large, but it was very much a film focused on introducing new characters and, in hindsight, giving Harrison Ford’s Han Solo a fitting sendoff. But for Star Wars: The Last Jedi, Luke is front and center, and he is far from the Luke Skywalker we last saw in Return of the Jedi.

As part of EW’s new cover story, Hamill, Daisy Ridley, and writer/director Rian Johnson teased what fans can expect from the Luke-Rey storyline in The Last Jedi, with Johnson revealing that it all began with figuring out why Luke was in exile to begin with:

“The very first step in the writing of this was figuring out why he’s on that island. We know that he is not a coward. He’s not just hiding because he’s scared. But we also know that he must know his friends are in danger. He must know the galaxy needs him. And he’s sitting on this island in the middle of nowhere. There had to be an answer. It had to be something where Luke Skywalker believes he’s doing the right thing – and the process of figuring out what that is and unpacking it is the journey for Rey.”

Hamill admits that he was taken off guard by Luke’s current state of mind:

“The fact that Luke says, ‘I only know one truth. It’s time for the Jedi to end…’ I mean, that’s a pretty amazing statement for someone who was the symbol of hope and optimism in the original films. When I first read it, my jaw dropped. What would make someone that alienated from his original convictions? That’s not something that you can just make up in an afternoon, and I really struggled with this thing.”

Ridley says it’s hard for Rey too, especially after the bond she forged with Han Solo, who was something of a father figure. Now she’s stuck on an island with “this grumpy guy” who very clearly wants to be left alone.

So it very much sounds like the Luke-Rey portion of The Last Jedi will be focused on Rey trying to turn Luke around, and Luke possibly training Rey in the Force. But it’s going to be an arduous road, as Luke is still traumatized by the last time he tried to train a promising young Jedi:

“[Luke] made a huge mistake in thinking that his nephew was the chosen one, so he invested everything he had in Kylo, much like Obi-Wan did with my character,” Hamill says. “And he is betrayed, with tragic consequences. Luke feels responsible for that. That’s the primary obstacle he has to rejoining the world and his place in the Jedi hierarchy, you know? It’s that guilt, that feeling that it’s his fault, that he didn’t detect the darkness in him until it was too late.”

But while The Last Jedi may or may not reveal Rey’s true parentage, the film does still leave some mystery as to where Luke’s been and what he’s done. Hamill says he spoke with Johnson to fill out the backstory that isn’t explicitly revealed in the film:

“There’s massive amounts of backstory that is left to your imagination and I couldn’t do my job without figuring out what that was. Since it’s not really important to the main story as a whole a lot of it is just for my own process. I talked with Rian about it and went into this elaborate scenario of what happened to Luke after the end of the Return of the Jedi.”

It’s possible we’ll get some of that backstory in Star Wars: Episode IX, which Colin Trevorrow is directing and which just hired Jack Thorne to do some rewriting on Trevorrow and Derek Connolly’s script. Or it’s possible Luke goes the way of Han Solo and kicks the bucket in The Last Jedi. Just as with The Force Awakens, Lucasfilm is keeping a tight lid on this film, which is for the best. And Episode IX doesn’t start filming until 2018, so the studio doesn’t have to confirm who’s coming back and who’s not until folks have seen The Last Jedi.

So yeah, the wait for Star Wars: The Last Jedi’s December 15th release continues to be excruciating.