Spoiling the Dark plot with Kotlin


As promised in my last post, it’s time to use our family tree DSL to spoil the plot of Netflix’s Dark series! 😈

To quickly recap, we have a small but functional (my puns are always intended) DSL for building a family tree in Kotlin:

The Dark family trees in code

The family trees are of course the focus of the series as they are revealed to us piecemeal; episode by episode, season by season. After watching it, I was overwhelmed with all the details and quickly gave up trying to fit it all together. Sure, I remembered some of the bigger points, but it makes a lot more sense after stepping through the Dark website to build the family trees below:

Let’s make a few observations about the above before using the power of code to uncover a few more:

  1. The Nielsen tree is the deepest, which highlights the family’s central role in the plot.
  2. As you should know if you’re reading this spoiler post, the years many people were born do not line up with their partners or children in many cases. We’ll get to that.
  3. Hannah Kahnwald appears in multiple places.

Analyzing the Dark family trees

Now that we have these family trees, what can we confirm about the plot from the data?

Who are the time travelers?

Since we have a hierarchy and birth years, we can traverse the tree and compare them to identify the time travelers. For our purposes, a time traveler is someone who is more than 30 years older than their partner or 70 years older than their children (Egon didn’t time travel, but Hannah did before their lovechild was born).

The code below is one way to implement this logic, but please let me know (or open a PR) if you have suggestions for improving something:

Who is their own ancestor?

Such a weird thought, right? Once again, I’m sorry to be the one to spoil this for you if you missed this juicy bit of the plot, but a couple people in the Dark family trees are their own ancestor. 🤯 While the approach for identifying time travelers involved recursively mapping the tree, we’ll need to collect the list of ancestors as we go to identify the self ancestors. We can do with with a data class, the fold function, and more recursion:

The big reveal

With the main() function below, we’ll print the answers to our time traveler and self ancestor questions:

Which gives us:

    Time Travelers:
    Mikkel Nielsen
    Hannah Kahnwald
    Silja Tiedemann
    Bartosz Tiedemann
    Elisabeth Doppler
    Noah Tiedemann

    Self Ancestors:
    The Unknown
    Charlotte Doppler


Now we have sufficiently spoiled the Dark plot with code! 🤓 You can find the full code here on GitHub.

Please reach out if you’d like to quibble about anything you think I may have gotten wrong. And if anyone has the galaxy brain to correlate the family trees above with the image below, please be my guest. I suspect the loops match up with time travelers and partnerships in the tree, but did not come up with any defensible theories.

Dark family tree loops