There are some secrets in TV and film that are never revealed, and fans of The Walking Dead long since gave up on finding out what caused the zombie apocalypse in the TV universe based on the Robert Kirkman comic book series. However in the post credit scene of Walking Dead: World Beyond, the spin-off series has done what Kirkman avoided doing in the entire run of the source material and given viewers the answer they have been waiting for over ten years since the show began: Exactly how did the zombie virus begin?

The Walking Dead is currently in the middle of a big change, with an expansion of the universe continuing while the main series comes to an end in 2022, but even with the endgame of the flagship series in sight, no one really expected any of the current shows to go ahead and reveal what caused the devastating zombie crisis in the first place. The mystery is one that sustained the early seasons of the show, with the first season coming close to offering some answers in the CDC episode, which would notably become an episode that creator Kirkman later said he regretted doing. That suggests that this latest turn of events is one that must have been pondered over for some time.

The final scene of the Walking Dead: World Beyond shows a biomedical facility in France, seemingly abandoned for some time although a former researcher has returned to attempt to discover a cure for the world-destroying virus. After being surprised by a cigarette-smoking survivor – The X Files vibes anyone? – the scientist says that she is going to end the apocalypse only to be told by the attacker, “End this? You started this.” On the wall are the words “Les Morts Sont Nes Ici”, which when translated roughly reads, “The Dead Are Born Here.” It is pretty clear that despite all the outlandish theories banded around over the last decade, the simple answer to the question of what caused most of world to turn into flesh-eating zombies is humans.

While this revelation doesn’t completely remove all the mystery from the creation of the virus, with the questions of why the virus was being developed and how it came to be released in the U.S. if it was being worked on in France still unanswered. For long-term fans of the series, this outcome is probably not too much of a surprise. Although some of the other options such as aliens or ancient gases leaking from the earth have been suggested, this is really the only outcome that would keep the show grounded in some kind of reality without it all becoming a bit too much of a “jumping the shark” moment.

One thing that is clear from the scene is that the cigarette man is linked to the outbreak, as at one point he is told “When it happened…When you did what you did,” by the scientist, suggesting that he was perhaps part of a group who attempted to sabotage whatever work was going done at the facility only to unleash the deadly contagion into the world. With Kirkman’s comic book series having already ended, and the final stories from the source material playing out in The Walking Dead’s final season, it looks like the show’s spin-offs have no intention of ending just yet and the exploration of the virus itself and its potential cure is where we are headed in at least one of the coming future series.