This section contains a summary of Babylon 5's story arc (the 5-year plotline) up to, but not including, "Walkabout." Note that this is chock full of spoilers!
The Babylon Project was conceived by the Earth government in the aftermath of the Earth-Minbari War. It was finally realized in Babylon 5, a diplomatic outpost created to promote peaceful conflict resolution. Even with such lofty goals, its galactic significance has quickly outstripped its founders' wildest dreams -- let alone their ability to control. Babylon 5's early years have been marked by a growing sense of foreboding, punctuated by successively more immediate threats to the station's safety. Yet as rising darkness nurtures galaxy-wide despair, the station begins to become the focal point for a number of tiny rays of light.
The gloom is made incarnate by the return of a mysterious ancient race known only as the Shadows. A thousand years ago they were beaten back to the rim of known space by an alliance which included relatively young civilizations like the Minbari, and a number of extremely powerful older races known collectively as the First Ones, who with the exception of the Vorlons have all passed beyond the confines of the galaxy -- presumably forever. On the rim, on dead deserted worlds like Z'ha'dum, the Shadows hid and gathered their strength for another assault ("In the Shadow of Z'ha'dum.") They do not act openly yet, but only through proxies like the human Mr. Morden, and the Centauri. What do they want? Only they know for sure. Chaos, it would seem, and control, and about two thirds of the galaxy.
It is ironic for a people as dedicated to hedonism and frivolity as the Centauri to become the facilitators of destruction and despair. Yet they are trapped by their dreams of former Empire and the vainglorious whims of individuals like Ambassador Mollari and the machiavellian Lord Refa. At first Londo thinks he can use his new friend Mr. Morden to further his own career, and is scarcely disturbed that the price is paid in Narn corpses. Disregarding all warnings, ("The Geometry of Shadows," "Knives") and the best chance for peace the Centauri have ever had, ("The Coming of Shadows") Londo oversaw the Centauri-Narn War from its inception as a border conflict ("Midnight on the Firing Line," "Chrysalis") to its culmination in the planetary bombardment of the Narn homeworld ("The Long, Twilight Struggle.") Yet as his dreams come closer to reality, his enjoyment of them ebbs, and it begins to dawn on him the extent to which it is he who is being used in the schemes of others.
The G'Kar who lied brazenly about the preemptive Narn strike against an undefended Centauri agricultural colony ("Midnight on the Firing Line,") is a far cry from the one who was ordered to petition Earth for sanctuary on Babylon 5 as the last surviving member of the Narn ruling body ("The Long Twilight Struggle.") In the intervening years he experienced a religious reaffirmation when he discovered on Z'ha'dum the ancient Enemy spoken of by the prophet G'Quon ("Revelations.") He learned futility by watching his warnings of the Enemy's return fall on seemingly deaf ears. And he learned humility from the greatness of his enemy's emperor ("The Coming of Shadows.") Perhaps these experiences have prepared him for the heavy responsibility he assumes of leading his people's struggle for independence in exile.
Signs from Earth have also grown markedly bleaker in just a few years. The anti-alien Home Guard ("The War Prayer,") the squelching of the Mars independence movement ("A Voice in the Wilderness,") and the increase in militarism back home ("GROPOS,") soon paled in comparison to the discovery of the conspiracy which led to the assassination of the Earth President ("Chrysalis," "Hunter Prey,") and the efforts of the insidious Ministry of Peace to eradicate the faintest whispers of dissent. In its most morally vacant act, the Earth government chose to sign a treaty of nonaggression with the expanding Centauri Empire ("The Fall of Night") rather than stand up for the sovereignty of the Nonaligned Worlds.
Whenever the Babylon 5 crew investigates the more disturbing situations arising from contact with Earth, they regularly find the Psi Corps lurking behind the scenes. Quite clearly the Psi Corps has no limits on the extent to which it will manipulate people in its efforts to obtain power ("Mind War," "Soul Mates," "A Race through Dark Places.") Among many who view them with suspicion, Commander Ivanova's hatred for the Corps is legendary; it is also a smoke screen to hide her fear that they will discover her telepathic latency. Within the Corps itself, there appears to be an even more dangerous, ultra-secret group operating under the code name Bureau 13 ("A Spider in the Web.") Among other acts of casual manipulation and destruction, they are likely responsible for planting the artificial personality in Talia Winters which was sent to spy on B5 and which wiped out Talia's true personality ("Divided Loyalties.")
Powerful, honorable, the Minbari almost annihilated Earth after their first encounter with humans, yet inexplicably surrendered in their hour of victory and subsequently helped sponsor the Babylon Project. Of the few humans and Minbari who know the complete story, many do not believe it. When the Grey Council war cruiser was poised over Earth during the Battle of the Line, a lone pilot attempting to ram their ship (Jeffrey Sinclair) was captured and interrogated ("And the Sky Full of Stars.") To their horror, the Council determined that Minbari souls were being reborn in human bodies. Besides the fact that Minbari refuse to harm their own, an ancient prophecy claimed that a great challenge would someday arise which could only be met when the two halves of the Minbari soul were joined. Thus, the Council ordered the Minbari forces to surrender ("Points of Departure.") Many Minbari, particularly among the warrior caste, still despise this decision ("There All Honor Lies,") and as the warrior caste grows more powerful on Minbar, there are signs of schisms appearing in the formerly coherent society.
The prophecy also mentions an individual who will lead the combined forces of Minbari and humans. So strong is her belief that she is this Chosen One ("Comes the Inquisitor,") that not only does Delenn refuse the Grey Council's selection of her to be the leader of all Minbari ("Babylon Squared,") but against its instruction to wait she metamorphoses into a human-Minbari hybrid ("Chrysalis," "Revelations.") Although permitted to remain as ambassador on B5, Delenn's confidence is severely shaken when the remaining Grey Council decides to remove her from their company ("All Alone in the Night,") and even further when she discovers that she is accepted by neither humans nor Minbari ("And Now for a Word," "There All Honor Lies.") She has only her faith in herself, the loyalty of Lennier and her growing bond with Captain Sheridan to depend on.
Delenn also appears to have the approval of the Vorlons -- although this is no easy burden. Enigmatic and extremely advanced, the Vorlons rarely seem to take the opinions of others into consideration when they act. They have visited many worlds, but not openly, perhaps to guide the species there, and perhaps to manipulate them. Kosh is willing to aid the few like Delenn and Sheridan who merit his attention ("There All Honor Lies," "Hunter Prey,") but they do not escape the encounter unscathed ("Comes the Inquisitor.") Since he arrived on the station, Kosh remained hidden inside his encounter suit for years. When he finally revealed himself, he appeared as a glorious being of light and lore -- different to each species who saw him. Very few realized that it was Kosh whom they saw, but most agree that they witnessed proof that the station is blessed ("The Fall of Night.")
After surreptitiously testing the attitudes of his crew for several months, Sheridan involved Ivanova, Garibaldi and Franklin in an extremely dangerous plot to investigate and root out the evil they see growing in the heart of the Earth government. At first they were all alone, with the exception of Sheridan's contact, General Hague. But as the Shadows come and darkness grows deeper throughout the galaxy, Babylon 5 has attracted unexpected allies for a great battle that looms heavily on the horizon. The first is Draal, who is the Minbari heart of the great machine and extremely powerful weaponry in the planet below the station. Assistance also comes from the embassy on Minbar, where former station commander Sinclair leads a growing army of mostly human and Minbari Rangers. In the vicinity of Babylon 5 the Rangers answer to Delenn and Captain Sheridan. Yet even with Draal and the Vorlons among them, by 2260 the fighters for the light seem pitifully few and weak compared to the pervasive and terrifying power of the Shadows.
"Matters of Honor" brought Marcus Cole, a Ranger, to the station; he led Sheridan and Delenn to a new ship, the White Star, a combination of Minbari and Vorlon technology. Pushing the White Star to its limits, Sheridan destroyed a Shadow cruiser. Londo attempted to sever his ties with the Shadows. Morden met with a Psi Cop, apparently far from the first such meeting.
The Centauri sent a replacement for G'Kar to the station in "A Day in the Strife" and threatened to persecute the families of G'Kar's supporters unless he gave up his exile and faced trial. Meanwhile, Ta'Lon, a Narn whose life Sheridan saved some months earlier ("All Alone in the Night") pledged to act as Sheridan's bodyguard. Londo arranged to have Vir sent off to Minbar as the new Centauri diplomatic liaison.
In "Passing Through Gethsemane," Lyta Alexander, the station's first telepath and the person who unmasked Talia's Bureau-13-implanted personality, returned from a stay on the Vorlon homeworld to become Ambassador Kosh's attache. The Vorlons appear to have modified her, possibly even enabling her to carry one of them inside her.
The conspiracy of light made its move against President Clark in "Voices of Authority" by releasing a recording of Morden and Clark planning Santiago's assassination. Ivanova located another race of First Ones and secured a promise of help in the fight against the Shadows.
G'Kar learned of Londo's involvement with the Shadows in "Dust to Dust." He was sentenced to prison for assaulting Londo, and was visited in a dream by Kosh, who posed as the Narn deity G'Lan.
In "Point of No Return," President Clark declared martial law on Babylon 5 after dissolving the Senate back home. An attempt by the Nightwatch to take over the station was foiled, barely, but Sheridan was forced to accept G'Kar's help and begin using Narn as station security personnel.
Despite his temporary victory, Sheridan was soon forced to cut the station's ties with Earth in "Severed Dreams," following in the footsteps of several secessionist colony worlds after the bombing of civilians on Mars. Delenn, meanwhile, confronted the Grey Council about its unwillingness to intervene in the spreading Shadow-initiated conflicts among the nonaligned worlds; the confrontation led to the shattering of the Council. A losing battle for control of the station was resolved only by the arrival of Minbari cruisers under the command of Delenn and other former Council members, who declared Babylon 5 under Minbari protection.
In "Ceremonies of Light and Dark," Sheridan admitted his growing affection for Delenn. Londo threatened Refa with death unless the Centauri broke off their relationship with Morden and the Shadows.
Vir returned to the station after being demoted for running an underground railroad for Narn refugees in "Sic Transit Vir."
Realizing that the station would be better off with more protectors than just the Minbari, Sheridan and Ivanova negotiated with several minor races to supplement the station's defenses in "A Late Delivery From Avalon."
Bester delivered a "Ship of Tears" to the station: a Shadow-bound cargo ship with hundreds of cybernetically enhanced human telepaths. Telepaths, the crew soon discovered, can disrupt the link between Shadow ships and their pilots.
Franklin resigned his post as chief medical officer in "Interludes and Examinations." Morden tricked Londo into vowing to crush Refa, and asking for Morden's help to do it. Sheridan convinced Kosh to mount a Vorlon attack on a small Shadow fleet. The Vorlons won the battle, but in retaliation, the Shadows killed Kosh.
In "War Without End," Ambassador Sinclair received a personally addressed letter from 900 years in the past. The note brought him to Babylon 5, where he led Delenn, Sheridan, and others in an expedition to pull Babylon 4 a thousand years into the past, when history recorded its role in the defeat of the Shadows. Draal, in the Great Machine, opened a time rift, and sent his aide Zathras with time-travel equipment and the chrysalis machine Delenn would eventually use to become half-human. During the time shift, Sheridan was pulled forward seventeen years to find himself in Londo's throne room on a ruined Centauri Prime. He and Delenn were thrown into a cell, where he learned that he had been victorious over the Shadows, but only to a point, and that he and Delenn had had a son, David. Londo, afflicted with a parasite called a "keeper" that monitored his every move, let the two of them go, then urged G'Kar to kill him before the keeper alerted anyone. The keeper awoke, and Londo and G'Kar died at each other's hands, leaving Vir to assume the throne. Meanwhile, on Babylon 4, the crew pulled Sheridan back to the present, and Sinclair stayed behind to supervise the station's transfer to the Minbari a thousand years before, as described in the letter from Valen -- who was actually a transformed Sinclair.