One of the best science fiction series on television is about to return. Before Silo premieres its third season on July 3 on Apple TV, it is worth revisiting how season two ended, what mysteries were revealed, the fate of its main characters, and why the upcoming episodes are expected to answer the question that has haunted the series from the beginning: how did humanity end up underground?

Based on Hugh Howey‘s bestselling trilogy, Silo follows a society of 10,000 people living inside a massive underground structure, with little understanding of what happened to the outside world. Across the first two seasons, Juliette Nichols, played by Rebecca Ferguson, gradually discovers that almost everything she was taught was built on a mixture of truths, half-truths, and carefully guarded secrets.

Season two picked up immediately after the events of the first season finale. After surviving her forced “cleaning” and leaving Silo 18, Juliette discovered that she was not alone. The devastated world contained dozens of other silos, and one of them, in particular, had become something of a ghost town.

It was there, in Silo 17, that she met Solo, played by Steve Zahn. Over time, the series revealed that the silo had been the site of a rebellion many years earlier. Its inhabitants managed to open the doors to the outside and died en masse. The only survivor, Solo, spent decades living alone among the ruins, carrying the trauma of a catastrophe he witnessed as a child.

While Juliette struggled to survive inside Silo 17, Silo 18 was moving closer and closer to collapse. Bernard Holland, played by Tim Robbins, tried desperately to maintain order, but his authority was beginning to crumble. Mechanical, led by Knox and Shirley, was approaching open rebellion, Robert Sims was starting to question the system, and even Sheriff Billings was increasingly uncomfortable with the lies holding their society together.

Meanwhile, Juliette had become a symbol of hope. For many residents, she was now a martyr and living proof that the truth was far more complicated than the leaders of the silo had ever admitted.

One of the season’s most important revelations came through Lukas Kyle. Turned into Bernard’s apprentice, he gained access to the Legacy, the secret archive reserved for the leaders of the silo. There, he began to understand the true scale of the system governing these underground communities.

Deep beneath the silo, Lukas discovered a massive door hidden under the water and made contact with an intelligence known as the Algorithm. The most terrifying revelation involved the existence of the Safeguard, a protocol capable of exterminating an entire silo through poisonous gas if things spiraled out of control. In other words, not even the leaders were indispensable. The system had been designed to sacrifice an entire community if necessary.

Eventually, Juliette found a way back to Silo 18. Her mission, however, was not to lead a revolution but to prevent a catastrophe. By cleaning the external sensors once again, she tried to show the inhabitants that the outside world remained deadly and that leaving the silo would mean certain death.

The revelation about the Safeguard shook even Bernard. For the first time, he realized that he, too, was merely a piece in a much larger machine. Desperate, he rushed to find Juliette, but the two became trapped inside the decontamination chamber amid fire and chaos, leaving their fate unresolved.

Yet it was the final scene that truly changed the scale of the story.

In its closing moments, Silo abandoned the present and traveled 352 years into the past. In Washington, long before the silos existed, Congressman Daniel Keene met journalist Helen Drew in a restaurant. What initially seemed like an ordinary conversation about a dirty bomb soon made it clear that something much larger was unfolding and that both of them were about to be drawn into a chain of events with catastrophic and irreversible consequences.

The duck-shaped PEZ dispenser seen in the scene was the same object discovered by Juliette centuries later, creating a direct connection between the past and the future.

It marked one of the biggest departures from the books. In Wool, the first novel in Hugh Howey’s trilogy, the story ends without revealing the origins of the silos. The series chose to bring forward elements from Shift, the second book, setting the stage for a far more ambitious narrative.

Other changes also stood out to readers. Judicial and Robert Sims were given much larger roles in the adaptation, Lukas became significantly more important, and Solo received more development than he did in the original material. The pace of the revelations has also been much slower than in the books, allowing the mysteries to unfold across multiple seasons.

Now, season three promises to unite both timelines.

According to the official synopsis, the new season will reveal the origin story set centuries earlier while continuing the events of the present. Juliette will survive the dramatic ending of season two but will return suffering from memory loss, just as Silo 18 attempts to recover from the rebellion and faces a dangerous new threat.

Meanwhile, during the so-called “Before Times,” journalist Helen Drew, played by Jessica Henwick, and Congressman Daniel Keene, portrayed by Ashley Zukerman, will uncover a conspiracy that ultimately triggers catastrophic and irreversible consequences.

Alongside Rebecca Ferguson, returning cast members include Common, Harriet Walter, Chinaza Uche, Avi Nash, Alexandria Riley, Shane McRae, Remmie Milner, Rick Gomez, Billy Postlethwaite, Clare Perkins, and Steve Zahn. New additions include Jessica Henwick, Ashley Zukerman, Laura Innes, Jessica Brown Findlay, Morven Christie, Reed Birney, Matt Craven, and Colin Hanks.

Already renewed for a fourth and final season, Silo is now entering the phase where it stops being merely a mystery about an underground society and becomes something much larger: a story about the choices that led humanity to collapse and about those who decided, centuries earlier, who deserved to survive.