Episode 17 of "Battlestar Galactica"
s02e02 Valley of Darkness

The Galactica has succeeded in reuniting with the fleet, but it has paid a terrible price: A Cylon computer virus has penetrated its computers. Col. Tigh knows from bitter experience what the Cylons are planning. The Centurions aren't going to blow up the ship... they're going to kill the crew by venting the ship's air and then turn its guns on the rest of the fleet. Only Lee whom Tigh despises for his "disloyalty" to Commander Adama and his small squad of marines are in position to stop the Cylon boarding party. Meanwhile, on Cylon-occupied Caprica, Starbuck and Helo break into her old apartment and fire up her old pickup truck. Light-years away on Kobol, Chief Tyrol and his crew return from their risky mission to get medical supplies for Socinus, only to realize that the wounded man isn't going make it.