S04E10: 'Revelations'

Admiral Adama returns to Galactica from the Basestar with D'Anna, who asks the Final Five Cylons to step forward. Tory does, but claims she only wants to go to the Basestar to give Laura Roslin medication.

Back on the Basestar, D'Anna takes Roslin and her men hostage and tells Adama that she will execute a prisoner every 15 minutes until the final Cylons are sent over. Adama is prepared to destroy the Basestar after Roslin earlier told him to do so, despite her being on board.

Saul Tigh confesses his Cylon status to Adama and suggests he be used as bait to spare the lives of the hostages. Adama is shocked, goes on a self-destructive rampage and drinks himself into a stupor.

The Cylon identity of Anders and Tyrol is soon revealed, and along with Tigh they are put near the Galactica airlock and D'Anna is told that they will die unless the slaughter stops.

Starbuck finds a hidden signal in her Viper with coordinates to Earth, following the suggestion of Anders that she inspect the vessel a bit closer. This fulfils the prophecy about Cylons and Capricans working together to find Earth, with D'Anna agreeing to form an alliance.

However, when they arrive on the planet they are shocked to find that it is in a ravaged, desolate state with no signs of life.