Spoilers for this episode and earlier episodes.
Jonas questions Hannah about Michael in 2019 after learning that his father was Mikkel. Hannah recalls meeting him at the hospital when she was young, but Jonas does not reveal what the letter has told him. He studies a new instruction on the cave map and prepares another expedition with the equipment the Stranger supplied. Meanwhile, Ulrich reopens Mads's police file and discovers that his family's account of the disappearance was incomplete.
Jana admits that Tronte was with Claudia on the night Mads vanished. Regina explains that Mads walked her home because Ulrich and Katharina had frightened her by tying her to a tree in 1986. Ulrich has also blamed Regina for the false assault accusation against him, but her denial leads him to check the records and identify Hannah as the witness. Katharina discovers Hannah's number repeatedly listed on the phone bill, while Aleksander learns of Regina's cancer diagnosis.
Martha performs as Ariadne in the school play, but breaks down onstage and is helped by Katharina. Jonas follows the red cord through the caves and uses the Geiger counter to locate a small door marked Sic Mundus Creatus Est. Passing through its tunnel takes him to a Winden where Mads is the missing child and Hannah is a teenager. Back in 2019, Ulrich compares the unidentified body's chin injury with a photograph and his mother's memory of Mads's childhood accident.