The Basement

Armin dreams of a weeping Colossal Titan, then wakes atop Wall Maria to a brutal accounting: nine Scouts remain, he has consumed Bertholdt, and the serum that revived him was denied to Erwin Smith. Levi owns the decision, explaining he chose this place for Erwin's death, while Hange privately concedes Erwin might have been the wiser pick. Neither asks Armin to replace the commander; Levi asks only that he honor what Eren and Mikasa risked to keep him alive.

Hange, Levi, Eren, and Mikasa then walk into the ghost town of Shiganshina. The basement key fails at the door, which Levi kicks in, and the room beyond looks like any doctor's study, so ordinary that Hange suspects the ordinariness was staged. A toppled cup leads Mikasa to a keyhole hidden in the desk. Eren's key fits it, revealing a locked drawer with a false bottom concealing three books. Fastened inside the first is an impossibly detailed family portrait; writing on its reverse identifies it as a photograph, light burned onto treated paper, and its author declares that he originates outside the Walls, in a refined human civilization that never perished.

In Trost, Nile recalls a young Erwin insisting the government buried the truth, and Zachary dryly suggests he apologize when Erwin returns, unaware the commander is dead. Crowds cheer the Scouts' capture of Wall Maria. The episode closes inside Grisha's account: as a boy he dragged his sister Fay past Liberio's security gate to watch an airship land, the day he would later call the one that taught him the truth of the world.

Armin learns the cost of his revival: Erwin was left to die, and Armin gained the Colossal Titan by eating Bertholdt.

The basement is opened after years of anticipation, with Eren's key unlocking a hidden desk drawer rather than the door.

Three journals and a photograph are found, proving an advanced human civilization exists beyond the Walls.

Wall Maria is declared retaken, and the surviving Scouts return to celebration in Trost.

Grisha's story begins, flashing back to the day he and Fay chased an airship outside the Liberio internment zone.

The Basement is the 19th episode of season 3 and the 56th overall, directed by Mai Teshima and Hitomi Ezoe from a Yasuko Kobayashi script, animated by Wit Studio and Production I.G. Japan aired it June 10, 2019; the US followed July 6. It adapts the chapter The Basement and the opening of That Day.

The episode resolves a mystery seeded in the very first episodes of the series, and its in-world information segment centers on the basement key itself, the object Eren has carried since the fall of Shiganshina.