Battlestar Galactica: Torn (Part 1)

Tigh and Kara begin to divide the crew between those who were on New Caprica and those who remained on Galactica, with troublesome results; Baltar convinces his Cylon captors to keep him alive by helping them locate Earth. When a Cylon ship finds an astronomical marker that will put the Cylons on the path to Earth, it becomes infected with a deadly virus, one that Baltar learns is ancient and might have been left behind by people from Earth.