Babylon 5 is a five-mile long space station located in neutral space. Built by the Earth Alliance in the 2250s, it's goal is to maintain peace among the various alien races by providing a sanctuary where grievances and negotiations can be worked out among duly appointed ambassadors. A council made up of representatives from the five major space-faring civilizations - the Earth Alliance, Minbari Federation, Centauri Republic, Narn Regime, and Vorlon Empire - work with the League of Non-Aligned Worlds to keep interstellar relations under control. Aside from its diplomatic function, Babylon 5 also serves as a military post for Earth and a port of call for travelers, traders, businessmen, criminals, and Rangers.
Lochley takes command of Babylon 5 and Byron petitions her for asylum aboard the station. An assassin pledges to kill Sheridan at his inauguration.
Londo collapses from a heart attack, and must battle with his guilt in a dream state. Delenn learns that Lennier is planing to leave Babylon 5 to join the Rangers.
A small world plagued by raiders begs the alliance for help. Garibaldi tries forming an intelligence unit of telepaths.
We see the action from the viewpoint of two maintenance workers as a race of savage aliens attacks the station.
Four rangers come from Minbar with a status report to Delenn, while a Downbelow racketeer decides it's time to get rid of Zack.
Bester arrives at the station to arrest the Downbelow telepaths, and Londo barely escapes an assassination attempt when the ship he was to be aboard explodes.
As more telepaths arrive at the station, the denizens of Downbelow start taking notice. Tensions build until one of the telepaths is assaulted, and the others decide to take revenge - against Byron's wishes. Meanwhile, Franklin tries to find out why the Hyach are hiding part of their medical history.
The Brakiri buy a part of Babylon 5 for a religious ceremony where the dead are supposed to return. Comedians Rebo and Zooty arrive to do a show on the station.
Londo starts to suspect that all is not right on Centauri Prime, when a good friend is murdered. On Babylon 5, Byron tries to force the council to give him and his telepaths a homeworld of their own.
The telepaths have barred themselves inside an area of Downbelow, and their telepathic tricks force Lochley to ask Bester for help. G'Kar finds an old friend locked in a cell in the Centauri palace.
More bloodhound units arrive and the fight with the violent faction of Byron's followers intensifies... until the rogues seize medlab - with Garibaldi and Franklin in it.
It looks like the Alliance will get a break in the investigation of the recent shipping line attacks, when a possible witness may have survived the latest attack and taken refuge on the Drazi homeworld. Garibaldi is sent to find him, but Intelligence Chief's alcohol problem complicates the mission. G'Kar returns to Babylon 5 to discover that his book has been published, and he is now a revered religious figure.
A telepath murders his roommate and escapes on a ship bound for Babylon 5. Bester is given the job of capturing him, and brings along two PSI Cop interns to show them how he works.
Delenn reassigns Lennier to a Ranger training mission on the border of Centauri space, hoping he can find some proof regarding the Centauri involvement in the shipping line attacks. Vir undergoes some dramatic changes when he learns that he is the new Centauri ambassador to Babylon 5.
Lennier investigates Centauri signals that may be connected to the attacks. Lyta tries to continue Byron's dream of finding a homeworld for telepaths. Lise visits Garibaldi only to discover he's drinking again.
The evidence collected against the Centauri is presented to the council of the Interstellar Alliance, and a boycott against the Centauri is issued. In reaction, the Centauri withdrawal from the Alliance and making it clear that they will circumvent the blockade by force if necessary.
Sheridan finally authorizes the White Star fleet to participate in the war. Delenn travels to Minbar to start a Minbari/Earth joint project to build a prototype White Star destroyer class ship. And Vir hires Franklin and Lyta to investigate why the Drazi don't return the bodies from destroyed Centauri ships.
As Centauri Prime is being bombarded, the Drakh, the real masters behind the war, reveal themselves to Londo. They force him to go along with their plan to alienate the Centauri from the Alliance, and use what's left as their new home.
Earthforce orders the arrest of Lyta for financing terrorism against the PSI Corp. Sheridan confronts Garibaldi about his drinking. G'Kar struggles with his growing mass of worshippers.
Tessa Holloran, former Number One of the Mars resistance, arrives with a warning for Lise and Michael - an assassin has been hired to kill them. Meanwhile, G'Kar gets ready to leave, though not everybody is happy about it.
It is near the end of 2262, and many changes are abound. Londo, G'Kar and Garibaldi have already left, and Franklin will be taking up his new position on Earth shortly. Finally, Sheridan and Delenn leave for Minbar, where the Alliance's recently finished headquarters are located.
Twenty years after his death and resurrection at Z'ha'dum, Sheridan feels his life force ebbing away, and invites some old friends for a final gathering.