What Is The Syndrome In Silo? Everything We Know So Far

Mystery box shows like "Lost" can be incredible, shows full of intrigue and mythology that raise questions and have you guessing while the character drama keeps you engaged. But mystery box shows can also get too bogged down by the mysteries themselves that they don't have much else to offer — like most of the "Lost" copies that came after that show's success.

That's what makes "Silo" so unique and great that Stephen King recommended it as a must-watched mystery box show. This is a sci-fi thriller with plenty of mysteries but because the characters can't just stop their lives and ponder these questions, we as the audience accept that we're not getting easy answers (at least not for a while). Together with just having memorable and well-written characters, the way the show doesn't make the mysteries feel urgent to the characters makes it easier to just follow them as they slowly unravel things themselves.

Based on Hugh Howey's book series of the same name, "Silo" takes place in a dystopian future where humanity was seemingly mostly wiped out and the survivors forced to hide in underground silos. Rebecca Ferguson stars as Juliette Nichols, an engineer-turned-sheriff who finds herself in the middle of a spider's web of conspiracies and mysteries about the past and present of the silos. It is not just one of the best shows on Apple TV+, but one of the best sci-fi shows of the last decade.

Among the many, many, many mysteries in "Silo," perhaps one that goes under many fans' radar has to do with the citizens of the silo, a strange disease they refer to only as "The Syndrome." What is it, and what causes it? This is what we know.

From the very start of the show we've learned that some residents of the silo suffer from an illness known as "The Syndrome." Though the nature of the illness is rather vague, there are some things we know for sure.

The first sign of The Syndrome is involuntary twitching, which then leads to limbs shaking, followed by pain and muscle spasms. If that isn't enough, the pain is followed by loss of balance and impaired movement. Finally, if the person suffering from The Syndrome isn't treated immediately, the infection reaches the brain and causes cognitive function to be reduced before the entire nervous system shuts down.

We get a few references to the condition in the earliest episodes of "Silo," but it isn't until episode 6 of the first season that we meet Deputy Billings (Chinaza Uche), who happens to have The Syndrome and keeps it hidden from everyone or else he'd lose his job as people with The Syndrome are not allowed to hold a position of authority and responsibility that can jeopardize the citizens of the silo. The most he exhibits is some occasional twitching, however, so it makes it easy for him to hide it.

Now, the series hasn't yet explained what exactly causes The Syndrome, but we hear from some characters that it is thought to be linked to a vitamin deficiency or blood disorder. We do know from Billings not isolating himself from his family that The Syndrome is likely not contagious, so what is it? The likeliest answer is that The Syndrome is a response to humans living underground for so long, entirely devoid of natural sunlight or fresh air. Prolonged exposure to the environment of the silo could cause The Syndrome. This theory is supported by an interview with Graham Yost, showrunner of "Silo," who outright spelled it out to SFX magazine, saying that "Human beings weren't meant to live like this. Talking about that with Hugh [Howey], we came up with something called 'the syndrome'. It's a neuralgic response to the pressure of living in these conditions." Yes, The Syndrome is entirely an original concept for the show, not really something found in Howey's books.

Based on Yost's comments, The Syndrome could even just be a psychological affliction rather than an entirely biological one. Or, perhaps, there's something else. We know from the end of season 2 of "Silo" that there is something called "The Safeguard Procedure" which unleashes poisonous gas to the silo, killing everyone in there if they ever dare to revolt. If however built the silos can do that, why not also create some sort of illness to keep the population at bay? Perhaps season 3 will hold more answers.