The Psi Corps and President Clark, whose government has discovered Shadow vessels buried in Earth's solar system, begin to harness the vessels' advanced technology. The Clark administration continues to become increasingly xenophobic and totalitarian, and uses a military incident as an excuse to declare martial law. This triggers a war of independence on Mars, which had long had a strained political relationship with Earth. Babylon 5 also declares independence from Earth, along with several other outlying Earth Alliance colonies. In response, the Earth Alliance attempts to retake Babylon 5 by force, but with the aid of the Minbari, who have allied with the station against the growing Shadow threat, the attack is repelled.
Becoming concerned over the Shadows' growing influence amongst his people, Centauri ambassador Londo Mollari attempts to sever ties with them. Mr. Morden, the Shadows' human representative, tricks him into restoring the partnership by engineering the murder of Mollari's mistress while putting the blame on a rival Centauri House. Open warfare breaks out between the Shadows and the alliance led by Babylon 5 and the Minbari. It is learned that genetic manipulation by the Vorlons is the source of human telepathy, as it is later discovered that Shadow ships are vulnerable to telepathic attacks. Displeased at the Vorlons' lack of direct action against the Shadows, Captain John Sheridan browbeats Vorlon ambassador Kosh Naranek into launching an attack against their mutual enemy. Kosh's deeds lead to his subsequent assassination by the Shadows.
Former station commander Jeffrey Sinclair returns to Babylon 5 to enlist the aid of Captain Sheridan, Delenn, Ivanova and Marcus in stealing the Babylon 4 space station and sending it 1,000 years back in time to use it as a base of operations against the Shadows in the previous Minbari-Shadow war. Undergoing the same transformation as Delenn at the end of Season 1, Sinclair transforms into a Minbari and is subsequently revealed to be the actual Valen of Minbari legend, rather than a reincarnation. Spurred by the reappearance of his assumed-dead wife (who now works for the Shadows), Sheridan travels to Z'ha'dum, the Shadow homeworld, in an attempt by them to recruit him. However he instead destroys their largest city in a kamikaze nuclear attack, and is last seen jumping into a miles-deep pit to escape the explosion. Garibaldi, during a fight with Shadow vessels, goes missing.
比利·鲍伯·松顿 黛米·摩尔 安迪·加西亚 艾丽·拉特 山姆·埃利奥特 雅库布·洛弗兰德 米歇尔·兰道夫 宝琳娜·查韦斯 凯拉·华莱士 马克·科利 詹姆斯·乔丹 科鲁姆·费奥瑞 盖·布耐特 文森特·杜瓦尔 约翰·W·希思 欧内斯特·马什 米里亚姆·西尔弗曼 斯特凡 哈普里特·阿罗拉 戈登·巴特勒
艾伦·旁派 贾斯汀·钱伯斯 钱德拉·威尔森 小詹姆斯·皮肯斯 凯文·麦克基德 莎拉·德鲁 卡特琳娜·斯柯松 卡米拉·卢丁顿 杰森·乔治 马丁·亨德森 嘉科莫·吉安尼欧缇 黛比·艾伦
唐·吉尔特 安东尼·J·亚伯拉罕 Tobi Bakare 伊丽莎白·布尔吉娜 米歇尔·格里尼奇 马克·霍尔登 金妮·霍尔德 香托儿·杰克逊 斯蒂芬·奥杜博拉 唐·沃灵顿
内尔·德贞 尼克·亨德里克斯 菲奥娜·多尔曼 安妮特·白兰特 马克·威廉姆斯 费迪南德·金斯利 麦米·麦考伊 Kojo Attah 赛奥汉·雷门 波佩·吉尔伯特 西妮德·马修斯 Kadell Herida 布莱恩·博维尔 路易丝·詹姆森 Molly Harris 马特·麦库伊 露丝·霍洛克斯