Juliette seeks refuge in an abandoned silo after a catastrophic war, believing herself to be the sole survivor, until unsettling discoveries challenge her solitude.

In the underground silo 18, chaos erupts after Juliette defies long-standing rules, leaving the residents grappling with the unthinkable.

Bernard turns to Judge Meadows for help. Billings begins to wonder if he's being lied to. Juliette finally meets the man in the vault.

Sims finds himself with a new position. Juliette learns Solo isn't being honest. Bernard and Lukas make an important discovery.

Bernard enacts a plan to root out Knox, Shirley, and Walker. Billings takes a stand. Solo saves Juliette's life and wants something in return.

Lukas is assigned a mission. Mechanical sends a powerful message. Juliette embarks on a perilous descent-and confronts a new danger.

Juliette discovers something's happened to Solo. Bernard makes an offer to Walker. Lukas meets with Salvador Quinn's descendants.

Billings' faith is shaken. Lukas heads to the down deep. Knox identifies the traitor. Juliette uncovers the truth about Solo's past.

In a post-apocalyptic world, a community lives deep underground in a giant silo, following strict rules they believe will protect them.