It's 1986, and Ulrich's brother, Mads, has been missing for a month. Confusion reigns as past and present intertwine.

Ulrich runs afoul of the law, Helge tries to dodge Egon Tiedemann, Claudia harnesses the cave's powers, and Katharina lashes out at Hannah.

In 1987, Ulrich seizes an opportunity. The kids return to the cave with the time machine, and Jonas learns of a loophole that could change the future.

In 2019, Jonas emerges from the cave into a strange but familiar world: the town of Winden, reeling from the recent disappearance of a young boy.