Finally promised peace after generations of war, the twelve Colonies of Man are betrayed by the robot Cylons. Their homes destroyed in a surprise attack, the last survivors of the human race strike out across the stars in ships, following the last surviving battlestar: Galactica.
The Colonial warriors of the Galactica attempt to bring food and comfort to the sick and dying throughout the ragtag fleet. But with their fuel and supplies running dangerously low, Captain Apollo proposes that they take the fleet through a dangerous region of space once mined by the Cylons, to the isolated mining outpost at Carillon.
The crew and civilians of the fleet find more than they bargained for when they visit the mining colony of Carillon, where tourists live in luxury and always win in the casino. Adama suspects an impending Cylon attack, and orchestrates a secret defense -- while Councilor Sire Uri plots to bring about the fleet's total disarmament.
Starbuck and Apollo discover an unending void of darkness in the Galactica's path ahead, but the only other path for the fleet leads past a Cylon listening post. Boomer and Jolly bring a virus back to the ship, which infects nearly every pilot on board -- forcing Adama to replace them with untrained women shuttle pilots.
The Galactica crew discovers the planet Kobol, the lost world from which the tribes of man originated, where Adama seeks to learn the original course of the thirteenth tribe. Baltar tries to lure the fleet into a new Cylon trap, which spells death for one of the crew.
Leading a Cylon patrol away from the fleet, Apollo is forced to land on a technologically less-advanced world, where the local leader maintains brutal power by the gun of a Cylon he has in his service.
As the fleet emerges into a new galaxy, Starbuck is sent on a reconnaissance mission. When his fighter is stolen, a signal sent to the Cylons and Starbuck imprisoned, the Galactica must consider whether or not to leave him behind.
The Galactica discovers the presence of a massive, Cylon-controlled weapon on an ice planet directly in their path, capable of annihilating the fleet. With Cylon base ships pressing at their backs, Adama sends a team of warriors and criminals to try and take out the weapon.
A group of human clones help a team from the Galactica to disable the massive weapon poised to destroy the fleet, while Adama is forced to try and make a run for it with the fleet. The criminals sent to help the warriors destroy the weapon turn on them in the hopes of escaping.
After a Cylon attack destroys the fleet's agricultural ships, Adama leads a mission to attempt to trade for grain seed at a human colony. But the locals manipulate the team into defending them from a group of murderous raiders.
An enigmatic and charismatic man arrives at the fleet, promising to meet all of their needs if they follow him as their new leader. Several viper pilots disappear after encounters with an alien ship.
Apollo and Starbuck escort Michael, Sarah, and their children to their new home away from the imperialist Alliance, but must protect them when the enemy arrives at their doorstep.
As Adama feuds with a council that is set on returning prisoners from the dangerous Alliance and seeking peace with them, Baltar and the Borillian Nomen plot their escape from the prison ship.
