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

Hannah takes her obsession with Ulrich too far. The stranger asks Regina to deliver an important package. Martha is torn between Jonas and Bartosz.

Ulrich looks to the past for answers and dredges up disturbing family secrets. Armed with new tools, Jonas probes the cave's murky depths.

Ulrich questions a frail and frightened Helge in the nursing home. Jonas searches for Mikkel, but the stranger warns him about meddling with the past.

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

Clausen and Charlotte interview Regina. The Stranger takes Hannah to 1987, where Claudia has an unnerving encounter and Egon visits an old nemesis.

Martha travels to 1888 to warn her friends about the 2020 disaster. Winden residents past and present search for their missing loved ones.