Sheridan must figure out how to destroy the implacable device before it's too late. An archeologist in his employ has stolen an ancient relic he believes to be the key to eternal life from the Soul Hunters, immortal creatures who capture and preserve souls throughout the galaxy. With the station under siege from the Soul Hunters, the explorer releases thousands of enraged souls from the relic who merge with others, attempting to taste life one more time. The former allies of the Shadows, the Drakh, attack Earth in revenge for the Earth-Shadow War that expelled the Shadow from our galaxy. Earth Forces succeed in defending the planet, but not before the Drakh spread a plague across the planet that will exterminate mankind in five years.
Earth becomes a quarrantined planet.
The Rangers are given the order to seek planets where a cure might be found. The starship, Excalibur, built of Minbari-Earth technologies, will respond to these leads to explore the identified planets and research a cure.