Serenity is the continuation of cult hit TV show Firefly. It follows the story of Captain Malcolm 'Mal' Reynolds and his crew on board the ship Serenity as they escort refugee River Tam through space...
When the Operative reviews Mal's file, it shows his birth date as 9/20/2468. 9/20/2002 is the date of the premiere of "Firefly".
Serenity was born out of the cancellation of the cult TV series Firefly. Whedon was unwilling to let the story fade, and set out to finish his story. He claims the story of Serenity spans what would have been season two and season three.
Serenity revolves around the story of Captain Malcolm Reynolds and his rag tag crew. Along the way as with many of Whedon's series, the story is actually of the frail recluse of River Tam. We learn of River's rescue from the Alliance by her brother Simon. That story was not explained in the TV series, but took center stage in the movie. Another thread that is explored is the origin of the dreaded Reavers.
River's secret hiding place aboard Serenity is soon discovered by an Alliance Operative who's mission is to recover and keep the secret that River as a physic might have gained from high level Alliance executives that visited the facility that she was kept in. Mal and his trusty gang all became attached to River and think of her as one of the family. Having tried and failing to thwart the Alliance in the war. Mal has no qualms about rebelling against the Alliance. After the secret is found out by the crew they all agree that everyone in the verse needs to know the truth.