Season 1: We meet Silja (Lea van Acken) in the final moments of season one, when she rolls up in a giant truck with other survivors in post-apocalyptic Winden. She welcomes Jonas to the future and knocks him out.
Season 2: In season two, we learn that Silja is Elisabeth's interpreter, as she knows sign language. When Jonas breaks Elisabeth's rules and tries to get into the ruins of the power plant, Silja helps him in exchange for letting her see what's inside. She's caught after Jonas travels through the dark matter by Elisabeth, and challenges her leader as to why the plant was off limits, now that she knows what exists there.
Season 3:
- Adam's World: In this reality, Silja is seen holding Martha captive on Adam's orders in 2053. She then travels to 1890 in order to preserve the loop. She meets Bartosz in the woods after burying her yellow suit from the plant, and the pair go on to marry. She's seen again in 1904, when she gives birth to a son named Hanno, and then again when she dies in labour with a daughter, Agnes, who is born in 1910. This is how we learn that Silja and Bartosz are the parents of the man who will become Noah. In a flashback to 1911, where Jonas/Adam lives at the Sic Mundus headquarters, Hannah introduces Silja to Jonas as his half sister. After Adam takes Hannah's life, he delivers Silja to "where she needs to be" in order for her to meet Jonas when he travels to 2052.
- Eva's World: Silja doesn't appear in Eva's world, but we know she has to exist in this reality in order for Agnes, Tronte, and Ulrich, and his kids to exist.
- Origin World: Without time travel, Hannah can never conceive Silja with 1954 Egon, so she doesn't exist.