Admiral Adama leads a group of volunteers aboard the Galactica into a dangerous mission to rescue Hera. With the decrepit condition of the ship, Adama understands that this will likely be the final mission of the Galactica. As the personnel face possible death in the battle, they recall key moments from their time on Caprica before the Cylon holocaust.
Despite Anders’ success at neutralizing the Cylon gun batteries, Adama’s volunteer attack force sustains heavy casualties. Cylon Raiders pursue the Vipers and Centurions board the Galactica. Kara attempts to decipher the meaning of Hera’s drawing and rescue the Galactica.
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.
The rebel Cylons and the Colonial humans react to Hera’s kidnapping while the physical condition of the Galactica continues to deteriorate.
Kara befriends a piano player who reminds her of her father. She also receives a mysterious drawing from young Hera Agathon. “Boomer” faces punishment for her support of Cavil in the Cylon civil war. She reconnects with Chief Tyrol and shares her visions of a peaceful life on Picon. However, her life on Galactica is much less tranquil.
Ellen returns to the Colonial Fleet with Boomer. Although Ellen is initially overcome with joy at seeing Saul Tigh again, she becomes troubled by the relationship between Tigh and Caprica Six. Ellen also learns that some of the Cylons want to leave the Colonial Fleet behind. Meanwhile, Baltar uncovers a dangerous situation among the civilians on the Galactica.
As Sam Anders recovers from his head injury onboard the Galactica, he begins to remember events from ancient Earth. Meanwhile, 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.
President Roslin seeks refuge on the Cylon base ship after Tom Zarek and Lt. Gaeta take control of the Galactica. Gaeta is determined to break away from Adama’s policy of cooperation with the Cylons but even he is disturbed by Zarek’s violent actions.
Adama continues with his plan to use Cylon drive technology on Colonial ships. The closer ties between the rebel Cylons and the humans sets off a violent uprising in the fleet.
Admiral Adama wants to outfit Colonial ships with superior Cylon jump drives to help the fleet find a new permanent home. As part of the deal, the Cylons ask for complete acceptance by the humans. Not everyone agrees with the plan. Tyrol uncovers some family secrets when he brings his ailing son to Doc Cottle for medical treatment. Meanwhile, Baltar rails against his God and stirs up his followers in the wake of their tragic disappointment over Earth.
Both the humans of the Colonial fleet and their Cylon allies fight against the emotion of overwhelming despair as they try to understand what happened to the 13th Tribe. Dee reconciles with her husband Lee Adama despite being devastated about the discovery of Earth. Kara finds a puzzling and disturbing clue regarding her identity.