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.
source: Wikipedia.org
source: Wikipedia.org
I liked the story, but I just couldn't help thinking that, in order for Mal to breathe up all the oxygen in a vessel the size of "Serenity" in that short a time, he would have had to have lungs bigger than Godzilla's. Also, I don't think that the temperature inside the ship would drop so low so quickly. But, you know, I'm the guy who counts how many times somebody shoots without reloading. Details are my passion.
Most of the excess heat and oxygen was vented or burned up by the fire.