When a fatal disease spreads over Bajor, threatening the entire
planet with extinction, Captain Sisko must accept aid from an
unexpected source: Ro Laren, Starfleet officer turned Maquis
renegade. Major Kira and Ro reluctantly join forces to track the
alien plague to its source -- even as the disease claims new
victims on "Deep Space Nine" itself. Dr. Bashir struggles
to find a cure, but the secret of the virulent invader may hide
deep in the shadows of Dax's past.