We return to Grisha’s accounting of the day he learned he was a prisoner, and always was. A prisoner of the oppressive Marleyans who confine all the Eldians to internment camps. A prisoner of history, for the Marleyans punish the Eldians for the crimes of their ancestors.
He’s a prisoner in his powerless child’s body, unable to save his little sister Fay from a terrible fate—being attacked and eaten by guard dogs—just for the crime of leaving the camp without permission. And he’s a prisoner to his father, who is a full-on collaborator who is happy to condemn his ancestors if it means being able to live out his humble life.
We also learn that the lands where the three walls that were the entire setting for Titan up to this point are only a tiny sliver of the world; in fact, everywhere Eren & Co. have ever known occupy a relatively small island called Paradis—the last refuge of King Fritz and the Eldians.
When Grisha learns the truth about Fay (confirming his suspicions), he joins an underground movement of “restorationists” bent on restoring once great Eldians—and of course, exacting revenge on Marley for their brutal oppression. They are aided by a member of Marleyan security, known only as the “Owl.”
That informant sends them the last surviving descendant of the Eldian royal family: Dina Fritz, and she and Grisha soon fall in love, get married and have a son, Zeke. But their attempts to indoctrinate him and make him the instrument of Eldian salvation fail miserably, as he turns in his own parents to save himself and his grandparents.
Grisha doesn’t blame his son—after all, he ended up building a prison for Zeke just as his father had tried to build for him: the prison of adopting the beliefs (and grudges) of one’s predecessors. But after thorough torturing, he, the other members of his cell, and Dina, are all sent to the island of Paradis, to be injected with serum to transform them into wandering Titans. Dina is transformed first.
Eren suddenly wakes up in a stockade in the present—he realizes he’s been connected with his father’s memories, such that it feels more like he’s been re-living Grisha’s experiences rather than simply having a normal dream. He and Mikasa are behind bars for their insubordination of Levi, but Armin, whom they defied Levi to save, is there with them.
Back in Grisha’s recounting, he finds himself at the boundary of the Titan penal colony, having just seen his friend and his wife transformed into mindless giant monsters, and the same officers he and Fay encountered the day she was killed are present with him. The mustachioed officer tells him he doesn’t feel remorse for the terrible things he does to Eldians because it was their ancestors who started the fight. Besides, life is more “interesting” if every day is lived like it’s your last.
As it happens, it is the last day for Mr. Mustache, as his colleague, Kruger, who was there back when Fay died and is here now, pushes him and not Grisha into the pit to be eaten by a Titan. Turns out Kruger is the Owl, and he cuts himself to transform into a lucid Titan, in order to demonstrate to Grisha what a Titan can do.
This was another trippy journey that vastly expanded the show’s universe and revealed more crucial answers about What This Is All About: a seemingly endless, vicious cycle of retribution between two races of men, neither of which can ever forgive the previous generations of the other; one ultimate prison, containing everyone in the world. So, when will Eren & Co. try to squeeze through the bars?