Out of Gas (Firefly)

"Out of Gas" is the eighth episode of the science fiction television series Firefly created by Joss Whedon. It differs stylistically from the rest of the series, in that it tells its story alternately in three timeframes: events in the present, events in the near-past that led to the present, and events in the past that led to the formation of Serenity's core crew.

After Serenity suffers a catastrophe that leaves her crew with only hours of oxygen, flashbacks show how Mal and Zoe acquired Serenity and assembled their motley crew.