Tyrol participates in the Circle, a secret tribunal on Galactica that tries and convicts in absentia those accused of collaborating with the Cylons during the Occupation.The passing sentences - administered without the knowledge of Roslin or Adama - begin to weigh on Tyrol's conscience.Baltar faces a similar jury among the Cylons, who must decide whether he is allowed to stay with them.
In a distant part of the universe, a civilization of humans live on planets known as the Twelve Colonies. In the past, the Colonies have been at war with a cybernetic race known as the Cylons.
40 years after the first war the Cylons launch a devastating attack on the Colonies. The only military ship that survived the attack takes up the task of leading a small fugitive fleet of survivors into space in search of a fabled refuge known as Earth.