Warning: Spoilers ahead for Bandersnatch.
While many paths involve Stefan (Fionn Whitehead) speaking to his therapist and require the viewer to make a choice between two options, only one path asks the viewer to take a single further action: dial a number and make a phone call. After Stefan finds the “Trauma Inception” patient files, he is filled with confusion and anger and kills his father. This isn’t the only path that leads Stefan to kill his father, but this one is slightly different. He calls his therapist and is asked about a number. If at this point you are wondering, “Wait, what number?” you’re not alone.
Reddit users successfully hunted down the correct sequence: 20541. Some first theorized that the numbers appeared in the flashbacks Stefan experienced at his therapist’s office. Others believed it had something to do with the phrase “All for one and one for all.” According to this walkthrough guide, the number is given to you through a montage of quick cut scenes. With anything Black Mirror, every little detail could — and likely does — mean something significant.
After inputting the numbers, Stefan is patched through to the office receptionist. The result, like several other iterations of the film, is Stefan going to jail and the game only doing marginally well.
That’s not the only use for this series of numbers. If you search for Tuckersoft’s website, you will find that it is under construction. You can still click on the job listings at the bottom, which will actually lead you to Netflix’s engineering jobs page if you click on the throwback ad. At face value, that is the only function of the website. That is, unless you know the right link. If you use this link instead, which contains the numbers 20541 in the url, you have access to the full website with all of its history, Easter eggs, and games based on past Black Mirror episodes with an ominous warning: “The people, places, and actions depicted in this game are based on true events.”