In "Valley of Darkness", a computer virus created by the Cylons shut down Galactica's power, but Lieutenant Felix Gaeta seemingly purged it. In "The Farm", Commander William Adama sentenced Specialist Cally to 30 days in Galactica's brig for killing the Number Eight copy who shot Adama (Boomer).
Gaeta determines that the Cylon virus is still active, is responsible for a series of malfunctions aboard Galactica, and threatens to take full control of the ship. Adama enlists Sharon's help. She confirms Gaeta's diagnosis and warns that a Cylon attack is imminent. Hundreds of Cylon Raiders and Heavy Raiders appear and hold formation, preparing to activate the virus. Forced to trust Sharon, Adama allows her to interface directly with Galactica's systems by inserting a fiber optic cable into her hand. Sharon helps delete the virus and broadcasts a virus of her own to the Cylon ships, rendering them helpless and easy pickings for the Vipers. Sharon is summarily returned to her cell.
Helo is ostracized by his crewmates for his relationship with Sharon. Haunted by memories of Boomer, Tyrol does not join the celebration of Cally's release. Tyrol and Helo argue about their respective relationships with Number Eight; the argument comes to blows. Inspired by Lee "Apollo" Adama's comment that "no one's expecting any miracles", Tyrol begins to build a new starfighter from salvaged parts.
Baah Pakal - A freighter among the fleet that had a pair of outdated DDG-62 engines that Chief Tyrol acquired to power his Blackbird stealth fighter in "Flight of the Phoenix ".Despite initial skepticism, crew members from throughout the ship join the project. At Helo's suggestion, Tyrol uses carbon composites for the exterior, making it stealth capable. The completed fighter, known as the Blackbird, makes a successful maiden flight with Starbuck as test pilot.
At the Blackbird's dedication ceremony, President Laura Roslin, who has just learned she has only weeks to live, praises the fighter's construction as "an act of faith." Tyrol reveals that the fighter is named Laura in her honor. Helo reconciles with his crewmates, and Tyrol visits Sharon in her cell.In the episode, the Number Eight copy being held on Galactica (Sharon) helps delete a computer virus created by the Cylons, and Chief Galen Tyrol builds a stealth fighter from spare parts.