The strain on the rag-tag fleet fleeing the relentless Cylons takes its toll, leading to a tough decision. 

Sharon wakes up soaking wet, covered in red stains, carrying an explosive. Six more bombs are missing from the locker. Who's controlling her and where has she been? 

When Captain Lee Adama recruits prisoners to retrieve an underground water supply from a desolate ice moon, several Galactica officers are held hostage by a charismatic anti-government leader. 

After a tragic accident on the Galactica kills 20 pilots, Adama orders Kara to train a new squad, but Kara is still wracked with guilt over Adama's son's death years ago. 

Kara has been hit by enemy fire and is missing. Lee and Adama are determined to rescue her, despite reservations from the crew about the use of precious resources. 

The crew's loyalties are put to the test when a Cylon suicide bomber infiltrates the Galactica and kills five people. Who let the bomber through security? 

Baltar is completely baffled when Number Six appears on the ship, posing as someone else. He is even more distressed when she accuses him of being the traitor. 

Starbuck discovers her own humanity in the most ironic place after she's ordered to torture a Cylon who claims he's put a bomb aboard Galactica. 

When Adama finds Tigh's wife, who was presumed dead, the paranoia on board reaches new levels of intensity. Everyone's a Cylon suspect. 

After months of fleeing from the Cylons, Adama decides to take the fight to the enemy. Starbuck and Lee must draw upon resources they never knew they had to become stronger and more capable leaders. 

President Roslin and her advisers realise that they must stop a convicted felon from becoming vice president. On Caprica, Helo gets a wake-up call. 

A supply patrol discovers a new hospitable planet; Baltar, Lee, and Kara find themselves in an awkward triangle. 

There's chaos in the fleet. The fighters battle with the Cylon ship, but can President Roslin find a path to Earth?