WARNING: The following article contains major spoilers for Attack On Titan Season 3, Episode 56, "The Basement."

Conspiracies and secrecy are as much a part of the fabric of Attack On Titan's dystopian world as its central human versus Titan conflict. Many of our brightest burning questions about what Titans are and how humanity's walled existence began have been answered by the smash-hit anime series' third season, a brazen but rewarding, efficient move for a medium known for testing audience loyalty by stacking episodes up by the hundreds.

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No mystery, however, has plagued Attack On Titan fans as much as what's in the basement. Since the show's earliest point, we've known that Eren's father, Grisha Jaeger, knew far more than he let on about the Titan situation, and whatever he knew was was clearly hidden away beneath the Jaeger family home, which he warned Eren not to go into until the time was right.

Before his death, Grisha entrusted Eren with the key for the basement, but the evacuation of their hometown of Shiganshina has kept his son, the Military Police and us at a frustratingly long distance from it since the show's first episode.

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The danger with long, drawn-out mysteries like this is that the resolution can struggle to live up to the hype. (Cough, cough, LOST, cough cough.) Not only does the future of the world in Attack On Titan rest on what's in this damn basement but, in a way, the future of the show itself. Does it deliver? We think so.

After successfully reclaiming Shiganshina, Eren, Mikasa Levi and Hange are finally free to head to the now-mythic location of the episode's title. As it turns out, the key Eren was holding onto for dear life isn't for the front door (which Levi unceremoniously bashes in), it's actually for a secret drawer in Grisha's desk. The drawer has a false bottom, which, when opened, reveals three books. After some painstaking stalling, Eren and Mikasa open the first book together to reveal… a photograph. A photograph of a family.

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Seems like a huge anticlimax, right? Until, and this is key, you remember that cameras aren't a piece of technology we've ever seen before in this world, a world that seems stuck in a pre-20th century era. This is confirmed by a puzzled Hange reading a note on the back of the picture explaining that the image is not an "illustration." The way she pronounces the word "pho-to-graph" says it all, really. Grisha was not from the world they know -- the only world they've ever known. It's a revelation that's as earth-shattering to the four of them as concrete evidence of the existence of aliens would be to us.

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This isn’t actually the first time something like this has turned up in the series. Remember in Season 2 when Ymir discovered some canned food written in a language only she could understand? Reiner, unaware of that she held the same Titan status as him at the time, starts to question her on this, but a sudden Titan attack on the castle they were holed up in prevents her cover from being blown. Now that we know Ymir is well-traveled beyond the Walls, it's possible that she picked up her linguistic skills from another more advanced human colony, or even originated from one.

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That advanced colony is glimpsed during the extended post-credits scene for Episode 56. We're shown a young Grisha and his sister Faye running through the streets of what looks like a city similar to any other in the show. Except, when the camera pans up, there’s an airship in the sky. He and his sister are also told to wear armbands by their mother and there are some throwaway comments about severe class segregation. So, conspiracy theorist Erwin did die for a meaningful reason. His theory about human life beyond the Walls is true.

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Of course, this answer opens up another basement's worth of questions about where we go from here. Will we see the Scouts -- of whom there are just nine left -- sent on a seek-and-discover mission? How did Grisha end up in Shiganshina? Does his original home still exist?

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The title of the next episode is "That Day," echoing the title of Season 1’s two-part premiere when humanity's century of peace was rudely interrupted by the Colossal Titan, so it's possible that last question will be answered. In any case, it looks like we’ll be getting a Grisha Jaeger origin story next.

New episode of Attack On Titan are available to stream on Crunchyroll and FUNimation, and air every Saturday night as part of Adult Swim's Toonami block.