Described as a "morally-compromising adventure" by Netflix, the film follows programmer Stefan in the '80s as he attempts to create a best-selling, text-based computer game inspired by a "choose your own adventure"-style novel given to him as a child. The book was originally written by a deranged artist who murdered his wife, so you can expect things to get dark, as only Black Mirror can.
As Stefan descends deeper and deeper into the world of Bandersnatch — in case you were wondering, "bandersnatch" is a fictional quick-moving creature first mentioned in Lewis Carroll's Through the Looking-Glass — the young programmer starts to experiment with pills, which alter his perspective of reality in drastic, dangerous ways.