Natalie Portman not showing up in the next Thor movie, Thor: Ragnarok, isn’t news. (Neither is the addition of Tessa Thompson to the cast in her absence.) We’ve known both of those things for a while now. The explanation for Portman’s absence hasn’t be fully revealed yet, though, and that’s something Marvel Grand Poobah Kevin Feige got into a little bit during his recent appearance on the Empire Film Podcast.

In the first two Thors, Portman played Dr. Jane Foster, an astrophysicist who discovers Thor (Chris Hemsworth) after he‘s banished to Midgard (Earth, to you Midgardians) by his angry dad-god (Anthony Hopkins). The two strike up a friendship and then later a romance, drawn to one another by their mutual interest in outer space and also their mutual hotness. (Can you blame them?)

There wasn’t any kind of breakup or explanation for why Foster would disappear at the end of Thor: The Dark World, but Portman’s a no-show in Ragnarok. So why no Port, man? Feige explains:

“There are only a couple of scenes on Earth in this movie; 80 to 90 percent takes place in the cosmos”

That is an eminently reasonable excuse why Jane Foster might not appear in the film. (although some are speculating that’s just the reason for writing out an actor who’s lost interest in the franchise). Either way, Marvel does seem to have a quietly brewing issue with the female leads of their movies. They mentioned Foster and Gwyneth Paltrow’s Pepper Potts in Avengers: Age of Ultron, neither was seen as their respective significant others went through serious emotional journeys and even a massive life change or two. The same goes for Captain America: Civil War, where a big part of Iron Man’s arc is motivated by his breakup with Pepper, who is mentioned repeatedly but never seen.

In that case, you might argue Paltrow’s disappearance works with Tony’s sense of isolation and loss at the start of the movie; we feel her absence as much as he does. But it’s going to get increasingly frustrating if Marvel has to write out these important supporting characters without a real resolution to their stories. So far, Marvel has done a fabulous job of casting their movies and threading people from one movie (and franchise) to the next. If they start to slip at that, well, it could be the Twilight of the Gods for a whole cinematic universe. Thor: Ragnarok opens in theaters on July 28, 2017.