A wounded man makes a desperate call, reporting that a gunman is holding a coffee shop hostage and shooting anyone he pleases -- but when the SWAT team shows up, the madman opens fire. Through flashbacks, a waitress serves an array of customers, all of whom are blissfully unaware of how their lives will be horrifically changed.

Season three reveals an origin story set centuries earlier, while continuing the saga of a dystopian society of 10,000 people living underground under mysterious circumstances. In the present, Juliette Nichols survives her forced "cleaning" but returns with memory loss as the silo recovers from rebellion and faces a dangerous new threat. Meanwhile, in the "Before Times," journalist Helen Drew and Congressman Daniel Keene uncover a conspiracy that pulls them into a chain of events with catastrophic, irreversible consequences.