As the premiere for the second season unfolds, Adama lay dying leaving Tigh in command. Lee and Roslin have been sent to the brig. An emergency jump goes wrong leaving the Galactica alone in space without the fleet.

A Cylon virus is interfering with Galactica's power supply, while Cylon centurions are heading for crucial systems. Somehow they must be stopped.

Journalist D'Anna Biers is making an item on the Gideon incident, when she's asked by Adama and Roslin to film daily life on Galactica.

The secret source in the administration has provided Tyrol with a list of all humans scheduled for extermination. Tyrol's wife Cally is on the list and he sets off to rescue her. Sharon Agathon has made it safely to the planet but they are ambushed by Cylons lying in wait. They realize they were betrayed and Anders finds damning evidence that points to the identity of the traitor. D'Anna Biers has been having strange dreams of late and an oracle tells her that the child Hera is alive and she will hold her in her arms. Roslin meanwhile assigns a squad of men to protect the child at all costs. The Admiral sends the Pegasus away with the few remaining civilian ships to continue the search for Earth.

The attack to rescue everyone on New Caprica begins. The Galactica encounters four rather than the expected two Cylon Basestars. The end appears in sight but they get help from a welcome but unexpected source. On the planet below, Tyrol and Anders lead the attack to free everyone from the prison. Anders finds Starbuck but she won't leave without Kacey. Her successful return to the Galactica results in mixed emotions. Colonel Tigh must decide what to do about his wife Ellen after she admits to giving the rendezvous coordinates to the Cylons. Hera doesn't make it off the planet.

Besides having to deal with the loss of Kara Thrace, the crew of the Galactica is also charged with the security surrounding the trial of Dr. Baltar and his defense attorney, who is replacing one lawyer that has already been killed.

The Fleet refuses to cooperate with Cylon engineers and Adama decides to put an end to it. He sends the Quorum a message stating that unless they wish to join Zarek in the cell, they get their people in line. However, Gaeta has already freed Zarek with the help of other would-be-revolutionists. They allow Zarek to leave Galactica on a raptor. He lands on Colonial One and enters a gathering of the Quorum. Meanwhile, Anders gets ambushed and captured. At the CIC, Gaeta cleverly manipulates everyone else until the time is at hand for the revolution to begin.

Roslin is on board a raptor en route to the Rebel Cylon Base Star, but Gaeta has ordered to engage and destroy it. The marines have used a stun grenade on Adama and Tigh. Roslin manages to get a wireless transmission out for everyone to hear and learn what Gaeta has done. She and the others barely make it to the Base Star, where she convinces Tory and the other Cylons to use the Fleet as a cover in order to prevent Gaeta from attacking it. She also believes that Adama will be able to save the rest of the Final Four. Temporarily safe, the Rebel Cylons start voting on whether they should just jump away and count their losses. Adama is brought before Gaeta and Tigh is thrown to the brig with Caprica Six, Anders, Athena, Helo and their child Hera. Zarek comes aboard Galactica on Colonial One with the Quorum. At Gaeta's insisting, Zarek agrees to put Adama on trial for treason, with Romo Lampkin assigned as his defence lawyer. There's just one problem: The Quorum refuses to recognize Zarek's authority. However, Zarek is hell-bent on following his "The truth is told by those left standing" maxim. Only Tyrol, who's alone, and Lee, whose with Starbuck, are Galactica's last hope.