As Kara miraculously returns to Galactica with the promise of directions to Earth, suspicion is cast on her identity. Baltar considers his new future when he is introduced to a group of people who practically worship him.
The Cylon models feud over the proper course of action after learning that the final five models are living as Colonials. Adama and Roslin debate Kara's fate after her confrontation with the President.
With Tyrol, Tory, Anders, and Tigh meeting in secret, a desperate and frustrated Cally suspects the Chief of having an affair -- only to discover the truth about him.
After suffering a major loss and slipping up on the job, Chief Tyrol goes through a major personal crisis. Baltar's sanctuary is assaulted, leading him to protest against the Colonials' gods. Tigh begins to see his dead wife in the face of the Cylon prisoner.
Tensions mount on board the Demetrius when Kara picks up Leoben adrift in a damaged Cylon ship, adding to the crew's distrust of her. Tyrol investigates Baltar's growing cult.
With the Demetrius crew at each other's throats, Kara takes Leoben to the wreckage of a Cylon base ship to follow the only lead she has left. During her cancer treatment President Roslin meets a fellow patient who is also dying.
Zarek assumes the presidency in Roslin's absence, triggering a power struggle within the fleet. Admiral Adama puts the fleet at risk in his search for Laura.
D'Anna's ploy to draw four of the Final Five out of the Colonial fleet leads to a hostage stand-off, with one of the Cylons offering himself as a bargaining chip. A critical clue to the location of Earth is discovered.
The fleet struggles with the repercussions of their discovery of Earth, and Lee must step up after President Roslin has a breakdown. Tigh discovers the identity of the final Cylon.
To move the survivors forward Adama proposes a more long-term alliance with the Cylon rebels. But Tom Zarek and the Quorum disagree, leading to a stand-off with the fleet left hanging in the balance. Tyrol learns a disturbing truth about his son.
Lt. Gaeta and Vice President Zarek move against Adama over his collaboration with the Cylons, launching an all-out coup and taking control of the fleet.
Gaeta and Zarek attempt to put Admiral Adama on trial to legitimize their coup, while President Roslin flees to the rebel base ship. Those loyal to Adama try and retake the ship.
A bullet lodged in Sam's brain brings out his latent memories of Cylon history and the Final Five, which he tries to share with the others before his surgery. The last Cylon is resurrected on Cavil's baseship, and fights against becoming a pawn in his twisted agenda.
The final Cylon returns to the fleet and is reunited with her loved ones, but her presence wreaks havoc between them. Baltar discovers that someone else has taken over leadership of his followers.
Kara meets a composer in the bar while she struggles to come to terms with what she found on Earth. The rebel Cylons ask to try Boomer for treason, leading Chief Tyrol to reconnect with her.
Galactica continues to deteriorate following the Cylon escape, forcing Admiral Adama to consider evacuating the ship. Helo and the crew react to Hera's kidnapping.
As the crew remember their old lives on Caprica, Admiral Adama launches a plan to rescue Hera from the stronghold of the Cylon civilization -- knowing that Galactica herself may not survive.
The crew of Galactica risks everything to rescue Hera from Cavil, joining forces with Cylon rebels for a direct assault on the enemy's home colony -- leading to a fateful, final showdown.
