With Adama out of action, Colonel Tigh takes his position as commander of the Galactica. Boomer is in jail, and the cat's out of the bag - she's a Cylon.

Tigh has to work with Lee to defeat a Cylon boarding party that threatens to take over Galactica and destroy the fleet.

Democracy is brought back to the fleet and soon with it come hardball politics and potentially deadly intrigue.

After Boomer's consciousness is downloaded into a new body following her death, she struggles with her new life on Cylon-occupied Caprica. Number Six is asked to help Boomer adjust to her new role in Cylon society.

Now on board Galactica, Baltar faces charges of treason. He contemplates suicide with the help of Number Six. Questions remain about his true identity. Is he a Cylon or isn't he? Apollo shows off the new drinking establishment on Galactica, Joe's Bar, to Tyrol. Apollo thinks about Kara and wonders whether his marriage to Dee is worth saving.

Tigh and Number Six take their first glimpse at their unborn child, Tyrol offers Adama Cylon technology in return for his fellow Cylons properly reintegrated into the fleet, and an attempted coup leads to a costly struggle to maintain civility.

As Sam Anders recovers from his head injury onboard the Galactica, he begins to remember events from ancient Earth. The Final Cylon struggles with the fallout from the Final Five's former plans. One of the humanoid Cylons vows to get revenge for being created in the image of Man. Tyrol informs Admiral Adama about the extensive structural damage on the Galactica.

The rebel Cylons and the Colonial humans react to Hera's kidnapping while the physical condition of the Galactica continues to deteriorate.

With Galactica on the verge of falling apart, Admiral Adama readies the ship for what could be its final mission, as Baltar's Six warns that humanity's final chapter is near.

Adama and the Galactica crew stake the survival of the human race on their plan to rescue Hera from the Cylon colony in this, the series finale.