Warning: Spoilers ahead for Silo season 2, episode 10!Silo character to successfully survive the outside world.

Silo season 2's ending flashback reveals more details about the events that go on to cause the post-apocalyptic world on display in the show's present timeline.

Silo Season 2's Flashback Confirms Theory That "Dirty Bombs" Destroyed The World

The Apple TV+ Show Reveals Conflict Between Iran & The United States

After showing what happens to Juliette in Silo season 2, the finale flips to a surprising flashback, depicting a time before the world was destroyed. In it, a young Georgia congressman meets a woman in a Washington D.C. bar for what he thinks is a date. Before he enters the bar, security scans him for radiation, revealing that a dangerous incident occurred in the US prior to Silo's flashback scene. When the congressman meets with his supposed date, Helen, they begin discussing where they were when "it happened," with the "it" being a "dirty bomb" orchestrated by Iran.

The flashback characters in Silo season 2's ending don't go into specifics about the Iranian bomb, but they do mention D.C. as the site of the incident. Helen then confirms that she works for The Washington Post and wants to meet the congressman to get answers from fellow US citizens regarding the existence and use of dirty bombs. Helen questions whether there are plans "to strike back against Iran and whether or not there really was a radiological weapon attack on the United States."

Silo season 2's flashback implies that the international conflict worsened, justifying Helen's worry on behalf of citizens.

Even at this point in the Silo timeline, there were questions about the conflict and the legitimacy of a "dirty bomb." Rather than one event that immediately impacted the entire country, Silo season 2's flashback implies that the international conflict worsened, justifying Helen's worry on behalf of citizens. Based on the condition of the outside world in Silo, it sure seems like the D.C. incident was just the beginning of a bigger war involving radiological warfare, making the country, and eventually the world, uninhabitable, at least presumably.

What Happened To The Outside World Has Been One Of Silo's Biggest Mysteries

Specific Details About The Apocalypse Hadn't Been Discussed In The Show

Silo takes place in a dystopian future; that aspect is instantly made clear in the Apple TV+ series. Still, the specific event that turned the country into an apocalyptic wasteland, causing people to survive in silos, has been a lingering mystery. By Silo season 1's ending, it's confirmed that the atmosphere is toxic and will kill anyone unless wearing specialized suits and Silo 18's special heat tape. While some silo inhabitants have questioned the validity surrounding the state of the outside world, Juliette confirms the truth when she returns to Silo 18 in season 2's finale.

Unlike nuclear bombs, which had been another popular theory linked to what destroyed the world in Silo, the use of dirty bombs disperses radioactive material over a large area, contaminating the atmosphere for long periods. The show has implied that Silo 18 has sheltered people from the outside world for over 300 years, with season 2 confirming the existence of at least 50 different silos. With the conditions still inhabitable on the surface for centuries, the existence of underground shelters can now be seen from a new perspective.

How The World Was Destroyed In The Silo Books

The Silo Book Series Takes A Prequel Approach With "Shift"

Warning: Spoilers for Hugh Howey's "Shift" arc, which covers novellas 6-8 in the series!Other than Silo seasons 3 and 4 will reveal about the world's history and destruction. However, Hugh Howey's books, on which the show is based, provide more insight into what happens to Earth's surface. Though Silo has made changes to the books, viewers can likely expect some aspects to be revealed in future seasons.

In Hugh Howey's "Shift" arc, the origins of the silo come into focus, revealing that the underground shelters are built in case of nuclear-related emergencies. Soon after, nuclear bombs wipe out Earth's surface in what was actually connected to World Order Operation Fifty (W.O.O.L.). After dangerous nanotechnology threatened humanity after becoming weaponized, Operation Fifty was put into place to cause a nuclear apocalypse meant to destroy the population aside from those in the silo shelters. The plan was to allow the remaining "good" nanobots to clean the surface until it was safe for the silo citizens to go back to the surface.

Silo has two more seasons to fully share their version of the books' complete story, seeing as the Apple TV+ adaptation is set to conclude with its fourth season. A portion of the remaining story will also bring back Helen and the congressman based on Silo season 3's plans to bring back Jessica Henwick and Ashley Zukerman as series regulars. Silo may not fully follow the books when it comes to Operation Fifty, but there are still plenty of aspects from before the major "incident" worth diving into.