Kara Thrace returns in a brand-new Viper to aide Galactica against a Cylon assault on a defenseless fleet, though her claim of finding Earth and who she is are held in doubt. As the awakened four of the Final Five struggle to figure who they are and what they are capable of doing, Baltar finds shelter among a commune who look to him for spiritual guidance.

Kara is prepared to turn friends into enemies in her feverish desire to guide the fleet on the right path towards Earth. The Cylons find themselves fracturing over the issue of what to do with the Raiders when they learn that the Final Five are in the fleet.

Cally's world is turned upside down when she suspects her husband is cheating on her. Meanwhile, Lee begins his career in politics, Kara leads a skeptical crew, and lines are finely drawn in the Cylon internal unrest.

Tyrol crumbles in the wake of Cally's death while Tigh finds himself drawn to Caprica-Six in a parellel to his own deceased wife. Baltar takes a stand for the religious freedoms of he and his followers.

The crew of the Demetrius begin drawing lines when Kara trusts a Cylon who offers the means of helping them find Earth. As Baltar's word begins spreading, he seeks to make peace with Tyrol.

The Demetrius allows a window for Kara to take a Raptor and a small party to the basestar to hear the Hybrid. Roslin befriends another cancer patient, terminally ill, who finds comfort in Baltar's message.

Galactica agrees to help the rebel Cylons unbox the Number Three models so as to reveal the identity of the Final Five while they, in turn, will be allowed to destroy the Cylon resurrection hub. However, alternate plans are secretly plotted as distrust still lurks within both sides.

With the President and a number of the fleet's pilots taken when the rebel basestar jumped away, Adama begins desperate but wreckless search efforts. At the same time, when it's obvious that the Admiral will not accept Zarek's assumed presidency in Roslin's absence, Lee seeks help from fallen lawyer Romo Lampkin to select someone else for the position.

As the rebel basestar jumps to the resurrection hub, the pilots onboard put their trust in the Cylons to help destroy their target while Roslin is faced with visions that could lead she and humanity to spiritual salvation.

When the rebel Cylons hold the colonials on their basestar hostage in exchange for the Final Five within the fleet, the secret four are confronted with the fear of revealing themselves in exchange for the good of the human race.

Everyone comes to terms with the discovery of a devastated Earth. As despair begins to spread, unlocked secrets of the ruined planet bring forth horrific discoveries, as well as revelations for the Final Five.

With the proposal of integrating the Cylons into the fleet, including allowing them on civilian ships to upgrade FTL drives, despondency from Earth turns into anger and distrust as Zarek sways the Quorum and other parties to take a stand over the alliance with the Cylons.

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.

Gaeta begins the process of trying Adama for his treasonable actions, but is conflicted with Zarek's own course of actions. Meanwhile, the small band of resistance on Galactica fights to regain control of the ship as Roslin attempts to maintain leadership as a refugee on the rebel basestar.

As Tyrol is assigned to repair Galactica's foreboding wear and tear, the bullet in Anders's brain unleashes a flood of memories that reveal the connection between the Final Five and the other Cylons. However, everyone is unaware that the opposing fraction of Cylons have been hiding Ellen since her resurrection about a year ago. And she has secrets to reveal as well.

Ellen reunites with the Cylons who vote to leave the human fleet, but Saul is left divided between the woman he once knew and the one carrying his child. Meanwhile, Baltar helps his followers look out for both themselves and others while Adama oversees the Cylon repairs to Galactica.

The Cylons wish to transport Boomer to the baseship to stand trial for treason, but Tyrol is driven by their past relationship to help her. Meanwhile, Kara befriends a piano player, helping him to compose an important piece of music.

As Adama is faced with the heartbreaking possibility of abandoning his increasingly deteriorating battlestar, Kara's connection to the mysterious music that ties her with Hera and the Final Five drives her to find out what she really is.

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....

Destinies that have long been in the making are finally decided when Galactica mounts its final mission in an effort to rescue Hera from the Cylon colony.