In the near future, breathable air is nonexistent. Virtually all of humanity has disappeared, and those chosen to reestablish society reside in a controlled state of suspended animation. Two engineers tasked with guarding the last hope for mankind struggle to preserve their own sanity and lives while administering to the vital task at hand.

When the initial Cylon attack against the Twelve Colonies fails to achieve complete extermination of human life as planned, twin Number Ones (Cavils) embedded on Galactica and Caprica must improvise to destroy the human survivors.