Silo: What happened in season three, episode eight - 'Gray Goo'?
Read a full recap of Silo's episode 'Gray Goo'
Last updated 14 hours ago
Episode eight of Silo season three was released on Friday 21st August 2026. Gray Goo starts just before the end of the previous episode, following Patrick and Lukas on the surface as they get shot at by an unknown person or entity.
Somehow the pair survive, with Patrick appearing to be unscathed, while Lukas has been shot in the shoulder. Meanwhile in the Before Times we learn more about the building of the silos and Per Stensen's (played by Colin Hanks) intentions. Read on for a full recap of the episode.
Episode eight - 'Gray Goo'
Arriving at the airlock for Silo 17, Patrick and Lukas bang on the door until the residents that Juliette left behind let them in, and they find ‘The Kids’. Jimmy from Silo 17 fixes Lukas’ radio, and they make contact with Juliette and Silo 18 (which we hear at the end of the previous episode 'Radio').
Juliette then takes over the radio, and tells Jimmy they need to ‘open up an investigation into his mum’, implying they need find the Fail-Safe, as he believed she died trying to stop it.
Meanwhile in the Before Times, Daniel and Helen arrive at the site where the silos are being built, before joining Per, Senator Thurman, her daughter Anna, Victor, and Charlotte for a meal where they discuss the building of the silos. The meal is interrupted as Charlotte has a funny turn and has to leave the discussion.
It’s at this meal that Daniel and Helen finally find out that the silos are being built to house people who will re-populate the Earth, after the impending apocalypse.
Back in Silo 18, Knox finds his estranged dad, as he tries to find out who has been transporting stolen goods from Supply – hopefully leading to find out who killed Orla.
Sheriff Billings, Deputy Hank with Knox's help get closer to finding out who murdered Orla, after Knox’s dad reveals more about an agreement he had with Harwood.
Meanwhile over in Silo 17, Patrick finds a door which he believes was welded shut from the inside. Eventually he gets the door open, where they find Jimmy’s mum’s body, in front of the Fail-Safe pipe. While Jimmy’s doesn’t want his mum’s body to be moved, after a conversation with Patrick he agrees and they find that the Fail-Safe pipe has been capped - presumably by his mum.
READ MORE: Silo phrases explained - All the key terms you need to know
Bernard draws up a plan of the silos, and tells Juliette how the Fail-Safe pipes are set up, before Juliette asks the question “Why build that in though, why do they need to kill a silo?”
Back at the meal in the Before Times, Daniel and Helen are offered jobs as part of ‘the project’, working on the silos, but decide not to accept, with Helen saying she’d "rather be blown into bits by a nuke, or turned into Gray Goo".
Just as Helen is about to leave on a helicopter, Daniel joins her saying: "I want to turn to Gray Goo with you", which prompts them to have their first kiss.
The episode ends with Juliette being arrested and taken to the cell where Robert Sims is being kept. Shirley tells the others she's been arrested, leaving Bernard saying "We have to cap the pipe".
What's happened in Silo season three so far?
Here's your chance to get up to speed on everything that's happened in Silo season three with our full recap.
Season three, episode one 'Who Are You?' recap
Season three, episode two 'It's All Good' recap
Season three, episode three 'A Dark Web' recap
Season three, episode four 'Whatever You Do, Don't Go Home' recap
Season three, episode five 'Memory' recap
Season three, episode six 'The Drive' recap
Season three, episode seven 'Radio' recap
Take a look through words and phrases that you might not know in Silo:
Going out to clean
Going out to clean in Silo its basically a death penalty. Residents of the Silo who go out to clean don't come back alive. They are sent out for two reasons, either because they break the law or they ask to go out voluntarily.
When they are outside, they clean the lens on a camera that displays on the screens in the cafeterias. Over time the lens gets covered in dust and debris from the toxic wasteland the residents of the Silo can see.
SPOILER! (Juliette is the only person so far to come back alive)
Up Top
The Silo consists of 144 levels, and they are connected by a single spiral staircase, there are no lifts. It is split into three main sections. Up Top is where the primary government offices, the Sheriff's station, and the surface airlock are situated.
The Mids
Below Up Top is The Mids, where many of the residents live along with the schools, and The Farm that grows food for the population. It also houses the Mids Medical, where Juliette's dad, a doctor, oversaw the nursery.
Down Deep
At the bottom of the Silo is the Down Deep. The people who live down there and keep the generator going rarely go up to The Mids or Up Top. There are many Deputy stations throughout the Silo, but the Down Deep Deputy Station is where Deputy Hank Murphy is charge. He is good friends with Juliette and Knox who work on the generator.
The Mines
Being sent to the mines is seen as a punishment for those who break the law. Iron ore was mined from The Mines, which are dirty and full of rats. Lukas Kyle is banished to The Mines for not reporting Juliette's relic.
The Digger Void
The area around the digger that was used to build the Silo is called The Digger Void. In the Digger Void is a camp made by George, where he hides a few relics, later Bernard is found hiding there, after many believed he had died.
Shadow
Someone's shadow is like their deputy, they are expected to learn from their mentor. In one of the early episodes Juliette gets a shadow called Terry Cooper. Juliette was previously Knox's Shadow, when she first transferred from The Mids.
The Algorithm
A select few from the Silo ever encounter The Algorithm, a voice that speaks to certain people about the Silo in a bright room with stepped walls. Although the subtitles call this voice The Algorithm it isn't referred to by the characters as such, and many don't know of its existence.
The Farm and 'going to the farm'
The Farm refers to the many farms in the Silo, where they grow crops and have animals such as pigs and chickens for the 10,000-strong population.
However, there's a slightly grim feature of The Farm, when members of the population die they can be buried in The Farm, so that their body's nutrients helps to feed the crops.
Before Times
Before the Silo was built was the Before Times - set in the near future (2040s). Not much is known about the Before Times in the first two seasons, with the third season beginning to explore why the Silo was created.
Judicial
Similar to the Sheriff, Judicial help to keep law and order in the Silo, they are responsible for enforcing The Pact and confiscating any relics.
Relic
Something from before the Rebellion. It's illegal to be in possession of a relic and knowing that someone has one and not reporting them can also be a punishable offence.
The Pact
The Pact is a book that the rules of the Silo are set out in. Several characters refer to The Pact throughout the series and how they must follow the rules.
The Rebellion
140 years before Silo is set there was a Rebellion when the residents of the Silo stormed the upper levels wanting to open the door to the surface and poison the entire Silo with air from outside. The Rebels burnt all the books, computer drives and anything from the Before Times.
Safeguard
A hidden pipe system which can flood the Silo with toxic gas. Use of it is designed to end the entire Silo's existence, but it isn't controlled by Silo 18, instead it is controlled by the overseers of Silo 1.