In 2019, a local boy's disappearance stokes fear in the residents of Winden, a small German town with a strange and tragic history.

When a grim discovery leaves the police baffled, Ulrich seeks a search warrant for the power plant. A mysterious stranger checks into the hotel.

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

Peter gets a shock. Jonas learns the truth about his family, but there are more surprises still to come. Helge makes a sacrifice.

Six months after the disappearances, the police form a task force. In 2052, Jonas learns that most of Winden perished in an apocalyptic event.

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

In 1954, a missing Helge returns, but he'll only speak to Noah. In 1987, Claudia brings the time machine to Tannhaus, and Egon questions Ulrich again.

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.

Armed with a plan to prevent the apocalypse, Jonas travels to 2019. During the Nielsens' anniversary party, Ulrich sneaks off with Hannah.

On the day of the apocalypse, Clausen executes a search warrant at the power plant as Jonas and Claudia use the time machine to connect past and future.

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

Across three centuries, Winden's residents continue their desperate quest to alter their fate and save their loved ones.

Claudia reveals to Adam how everything is connected — and how he can destroy the knot.