Ever since Nick Fury first showed up at Tony Stark’s house to plug the Avengers Initiative at the end of 2008’s Iron Man, post-credit scenes have been a staple of Marvel Cinematic Universe movies. Sometimes they’re just a little gag, a bonus for sitting through the credits, like the sequence of the Avengers silently eating shawarma together in a partially wrecked New York City takeout after the catastrophic fight in The Avengers, or the Howard the Duck cameo after Guardians of the Galaxy. Much more often, though, they’re specific teases for a Marvel movie that’s coming up on the release docket, from the initial visit to Wakanda at the end of Captain America: Civil War to tease events in Black Panther to the various scenes introducing the villain Thanos long before he turns up in Avengers: Infinity War.

The Avengers: Infinity War post-credits scene is no exception. Anyone sticking around through the film’s credits, hoping for some bright spot to leaven the film’s grim ending, instead got an oblique reference to a Marvel movie headed to theaters in 2019. The tease will also certainly be relevant to the still-untitled Infinity War sequel, but that’s still more than a year and a couple other Marvel movies away. But for those who didn’t immediately recognize the significance of what they saw onscreen, here’s a rundown. Significant spoilers for Avengers: Infinity War ahead, obviously.

What happens?

In that final sequence, the havoc Thanos has wreaked on the universe with the Infinity Gauntlet has spread across Earth. Nick Fury (Samuel L. Jackson) and Maria Hill (Cobie Smulders) are driving when people start breaking down into drifts of grey ash, resulting in crashing cars as drivers evaporate, and a helicopter crashing into a building. As Maria evaporates, Fury pulls out and activates a small device. Then he, too, crumbles into soot. The device, which looks somewhat like an old pager, continues to attempt a connection. Then a low-resolution starburst icon appears on its display, surrounded by red and blue lines.

What does it mean?

It helps to know what that symbol is — it’s an abstract version of the insignia of Captain Marvel, a hero who hasn’t yet appeared in the Marvel Cinematic Universe, but who’s slated for her own MCU movie in March 2019. Fury is clearly contacting Captain Marvel to alert her to the situation on Earth — a move that both sets up her solo film, and her eventual reappearance in the Infinity War sequel, as an important part of the solution to the Thanos problem.

Why would Fury call her?

Two reasons: they have significant history together, and she may be the last power capable of stopping Thanos. Captain Marvel, the upcoming movie, is a prequel set in the 1990s, focusing on how Air Force pilot Carol Danvers (Brie Larson) gained super powers after an accident that compromises her DNA by merging it with an alien’s. Fury, as part of the military, is part of the behind-the-scenes team that knows her and works with her. (As a bonus, it’s set in a period before he started wearing an eyepatch — though given the economy of action that the MCU works under, it’s a fair bet that this movie will actually show the events that cost him his eye.) So they’ve known each other for decades, and it’s logical that if anyone would have a method to reach her, he would.

In addition, it’s possible that she has a particular responsibility to fix the situation. Nick Fury has been part of the government organization S.H.I.E.L.D. since Stan Lee and Jack Kirby first introduced the group in a 1965 issue of Strange Tales. S.H.I.E.L.D. is responsible for dealing with paranormal and supernatural issues that endanger the people of Earth, but they have a counterpoint organization, S.W.O.R.D., which specifically tackles alien incursions against Earth. That group was created in 2005 by Joss Whedon for Astonishing X-Men. And in 2015, Agent Carter showrunners Tara Butters and Michele Fazekas launched a Captain Marvel comics storyline that had Carol Danvers put in charge of S.W.O.R.D. Depending on what kind of continuity the MCU movies are playing with, it’s entirely possible that Captain Marvel is directly responsible for dealing with alien threats to Earth.

And on top of all that, Kevin Feige has described Captain Marvel as the MCU’s “most powerful hero by far… If you had the collector cards of the Marvel characters and you could see the power levels, she would be off the charts compared to anyone that we’ve previously introduced in a film.” It seems like calling her in is a kind of Hail Mary in a situation that’s more dire than anything Earth has faced in this storyline so far.

Why hasn’t Fury called Captain Marvel in before?

If it’s true that Captain Marvel is working with or running S.W.O.R.D., why didn’t Fury call her in when The Destroyer took on S.H.I.E.L.D. in Thor, or when the Chitauri were dropping through a wormhole to invade Earth in The Avengers? That’s not entirely clear yet, but Captain Marvel may have some of the answers. Obviously the real-world answer is that Marvel Studios hadn’t yet worked out where her character fit into the bigger picture — her film has been in development since 2013, and has apparently mutated repeatedly since the first hints that it was in planning — but the question is whether there’s a good in-universe reason.

Certainly another possibility is that she isn’t part of S.W.O.R.D., and isn’t nearby, waiting to defend Earth from aliens. Given Carol Danvers’ various adventures since she was first introduced in 1968 — and since she first became Ms. Marvel in 1977 — there’s a lot of history to draw on, and a lot of key Marvel elements she’s associated with that we haven’t seen in the movies yet, but that could become key to later major Marvel plotlines.

What could Captain Marvel bring to the story?

The big elements she seems to be bringing to the MCU are the Kree and the Skrulls, two alien races that play major parts in the larger Marvel comics continuity. The alien whose DNA gave her powers in the comics, Mar-Vell, is a Kree hero. (Jude Law has been cast in the role for the 2019 movie.) The shapeshifting Skrulls have been tapped as the major antagonists in the Captain Marvel movie, which could lead the movies into the mega-crossover plotline of the Kree-Skrull war. Bringing these two combative races into MCU continuity sets up a huge number of potential plotlines from the comics.

But it’s also possible that Marvel Studios will be specifically drawing on Mar-Vell’s history to deal with the issues created by the end of Infinity War. In one 1970s plotline, Thanos got his hands on the Cosmic Cube, one of a series of devices (possibly created by the Skrulls, at least in one storyline) that effectively grant wishes. Thanos uses it to take control of the universe, but Mar-Vell destroys it — retroactively changing everything Thanos wished for, and restoring the universe to its rightful place. Infinity War 2, whatever it’s called, won’t necessarily be using that exact plot to resurrect its dead heroes and set its universe to rights. But expect some kind of walkback of what we saw in Infinity War, because there’s no way the MCU is going to leave characters like Star-Lord, Black Panther, and Spider-Man dead — especially not with sequel movies for all of them already on Marvel’s schedule.

Why is that Captain Marvel pager so old and janky-looking?

Maybe she’s currently off with the Kree, and it’s a piece of Kree technology, and that’s just how their super-advanced tech happens to look. Maybe it’s a piece of hyper-sophisticated alien tech disguised to look like something more familiar from our world. Or maybe it’s just a leftover artifact from Nick Fury’s time with Captain Marvel in the 1990s. This, also, may be a question answered when Captain Marvel hits screens in 2019. As with all Marvel teases, the answer may be obvious once the movie it’s referencing has actually made it to theaters, but for now, it’s meant as a deliberate conversation-starter, a way to keep fans occupied while they fret over the end of Infinity War and start anticipating what comes next.