Warning: this article contains spoilersAfter six episodes of slowly bringing its two timelines closer together, Silo season three finally offers one of its clearest glimpses yet of how the world above ground may eventually become the one inhabited by Juliette Nichols (Rebecca Ferguson) centuries later.But before then, there is the small matter of saving Silo 18.Episode seven opens with Lucas Kyle (Avi Nash) and Patrick Kennedy (Rick Gomez) preparing for their dangerous journey to Silo 17, a mission approved by The Algorithm after Juliette argued that its surviving residents could still be rescued.There is already reason to be suspicious. In episode six, The Algorithm privately told Camille Sims (Alexandria Riley) that neither man was expected to make it to Silo 17 alive.Those fears intensify when their planned dawn departure is suddenly brought forward. Once outside, Lucas reports that conditions are more abysmal than expected. “We see the damage. It's way worse than we imagined,” he tells those listening inside Silo 18.Then comes what sounds like gunfire, followed by silence.The Algorithm soon informs Camille that Lucas and Patrick have been “neutralised”. More worryingly, it tells her that The Safeguard – the mechanism capable of wiping out everyone in Silo 18 – cannot be prevented.From left, Avi Nash, Rick Gomez and Rebecca Ferguson in Silo season three. Photo: Apple TVShow caption: From left, Avi Nash, Rick Gomez and Rebecca Ferguson in Silo…The news comes as Juliette learns the threat inside her own silo is becoming more urgent. Robert Sims (Common) tells her the memory-suppressing chemical has already entered the water supply, meaning thousands of residents are unknowingly consuming it.With time running out, Bernard Holland (Tim Robbins) presents Juliette with an impossible choice. Their plan is to destroy Judicial, which controls the system being used to distribute the memory-suppressing chemical and the outlets capable of releasing toxic gas. But destroying it could cause enormous collateral damage, potentially killing about 1,000 people.Doing nothing carries devastating consequence. With the drug already contaminating the water, Silo 18's population could gradually forget what has happened and, crucially, what they have been fighting against. Juliette reluctantly agrees to proceed.But just as the bombs are about to detonate, a voice suddenly crackles over the radio. It's Patrick. Despite The Algorithm's assertion that he and Lucas had been neutralised, they have made it to Silo 17 alive.Ferguson and Tim Robbins in Silo season three. Photo: Apple TVShow caption: Ferguson and Tim Robbins in Silo season three. Photo: Apple …The revelation raises an immediate question: if The Algorithm was wrong about Lucas and Kennedy, what else might it be wrong about?Meanwhile, the Before Times storyline delivers some of the episode's biggest developments.Back at the hangar where episode six ended, congressman Daniel Keene (Ashley Zukerman) is stunned to discover his sister Charlotte (Jessica Brown Findlay), although she appears distant and disorientated following the Iran mission that left her without her memories.Daniel and journalist Helen Drew (Jessica Henwick) are told they can learn what is described as the “world's biggest secret” – but only after signing non-disclosure agreements.Enter Per Stensen (Colin Hanks), introduced as the richest man in the world. Brash and immediately difficult to trust, he attempts to persuade the pair with money, while Daniel discovers Charlotte has already signed.Daniel eventually agrees, while Helen remains reluctant until Senator Rosalind Thurman (Laura Innes) insists: “This really is about saving the world.”Their journey takes them to Atlanta to an enormous tract of land spanning about 300,000 acres. Stensen boasts that he bought the land from farmers by giving them generational wealth, before delivering the episode's most ironic line: “Billionaires. They ruin everything.”Silo season three, episode seven ending explainedAlexandria Riley as Camille Sims in Silo season three. Photo: Apple TVShow caption: Alexandria Riley as Camille Sims in Silo season three. Photo…Episode seven closes in the Before Times with perhaps the clearest connection yet between the Washington storyline and the underground world where Juliette lives.Daniel and Helen are brought to Stensen's vast property, where enormous drilling machines can be seen boring deep into the ground. The series stops short of explicitly identifying what is being constructed, but after three seasons spent inside enormous underground bunkers, the implication is difficult to miss: we appear to be witnessing the beginning of the silo project.It would also explain why Stensen has acquired such an enormous area of land and why Thurman believes their work could “save the world”.The question now is what they believe the world needs saving from.