Commander Adama (Edward James Olmos) is keenly aware that morale is at a low point after what he terms months on the run with little to show for it but casualties and deteriorating conditions. Chief Tyrol (Aaron Douglas), still haunted by his memories of the first Cylon Sharon, is in a bleak mood. He verbally spars with Capt. Lee Adama (Jamie Bamber) and gets into a drunken punch-up with Helo (Tahmoh Penikett), who remains romantically committed to the current avatar of Sharon (Grace Park). After sending one more dilapidated Viper to the scrap heap, Tyrol vents his frustration by attempting to build a new plane from salvaged parts. His seemingly impossible mission generates cynicism at first, then growing respect and eventually a full team effort that pulls in even the skeptical Col. Tigh (Michael Hogan). Meanwhile, a Cylon virus penetrates the Galactica's computers. It wreaks havoc by creating dangerous power surges, an unscheduled engine ignition and a near-fatal oxygen shutdown. Sharon, who remains imprisoned in the Galactica's brig, is enlisted to defuse a threat that she immediately recognizes as the prelude to a Cylon assault. Adama orders the fleet to jump to new coordinates while the Galactica stays behind to wipe the virus from its computers and contend with a massive assault by more than 200 Cylon Raiders. Though Sharon’s motivations are in doubt - do the Cylons really pose a danger to her unborn child, or is she working some deep Cylon agenda? - she turns the computer virus against the attacking Cylon fleet and enables the Galactica and her vastly outnumbered Viper squadrons to win the battle without taking any casualties. Flush with the thrill of victory, the crew's spirits soar higher still when Tyrol's lab project takes flight - as a powerful new model of stealth ship that they name the Blackbird.