This section contains a chronological summary of Babylon 5's story arc (the 5-year plotline) as it has been presented so far. Only certain episodes, believed to be of some significance, are mentioned. Note that this is chock full of spoilers!

The pilot, "The Gathering," is set in the year 2257, introducing station Babylon 5 which has recently come online. The last of the ambassadors, Kosh, arrives on the station, prompting an assassination attempt. Sinclair is framed for the attempt, but is eventually cleared when the real culprit -- a Minbari -- is discovered. Many mysteries are introduced: Sinclair's missing 24 hours on the Battle of the Line (with the announcement by the Minbari that "there is a hole in your mind"); the mystery of Kosh, seen only by the doctor and the telepath; and the disappearance or destruction of the previous four Babylon stations.

Season one begins with "Midnight on the Firing Line," about 6 months later. Lt. Cmdr Susan Ivanova has recently taken over the second-in-command post; we learn of her dislike of the psi corps. The doctor and telepath from the pilot are no longer on the station. A Centauri agricultural outpost is attacked without provocation by the Narns. (In broad strokes, this episode portrays the Narns as the "bad guys" and the Centauri as wishy-washy comic relief.) Luis Santiago is reelected President of the Earth Alliance.

A "Soul Hunter," a member of an order which collects and preserves important souls, finds himself on the station, and attempts to collect Delenn's soul prematurely. We learn the importance of the Minbari soul, and that they prevented a soul hunter from taking the soul of their great leader Dukhat, so that his soul would be reborn into the next generation. Delenn is called Satai by the soul hunter, which prompts Sinclair to wonder if something is going on, as Satai is the title used my members of the Grey Council, the Minbari ruling body and highest religious authority.

In "Mind War," two Psi Cops -- P12 level telepaths, including Bester (played by Walter Koenig) -- come to the station in search of telepath Jason Ironheart, who has achieved telekinetic abilities and is transforming into something more than human. He warns Sinclair that the Psi Corps are starting to pull the strings in the government back on Earth. When Bester's partner is killed, Sinclair makes a new enemy. Before departing, Ironheart gives Talia a gift: telekinesis, and maybe other abilities as well.

"The War Prayer" introduces members of the Homeguard, an anti-alien establishment back on Earth.

"And The Sky Full of Stars" explores what happened to Sinclair on the Battle of the Line, 10 years before in the Earth-Minbari War. Interrogated and forced to relive the battle, we see Sinclair ram a Minbari Cruiser, only to wake up on board, interrogated by the Grey Council. He recognizes Delenn as one of the Grey Council. After escaping from his interrogators, he chooses not to reveal to Delenn that he remembers part of his missing 24 hours.

"Deathwalker" is a notorious war criminal from the Dilgar War, fought by Earth and others several decades earlier. She has a substance she claims grants immortality -- but only at the cost of another's life. The Vorlons destroy her ship to prevent Earth from gaining the secret of immortality.

"Survivors" takes Garibaldi back into his alcoholism as he is accused of sabotage. The real culprit is the Homeguard.

"Signs and Portents" deals with an attack by raiders on the station. The B-story, in which Londo acquires the long-lost symbol of his empire, the Eye, is more important. A mysterious, polite man named Morden inquires "What do you want?" of the alien ambassadors, and seems to like Londo's response -- for the Centauri to reclaim their lost empire -- the best. The Eye is captured by the raiders, who are destroyed by a mysterious ship that appears out of the shadows. Morden returns the Eye to Londo, "from friends you don't know you have."

In the two-parter, "A Voice in the Wilderness," it is discovered that the planet below B5 is not as dead as it was thought. The Mars colony breaks out in rebellion. A dying alien is found controlling vast, tremendously powerful machinery on the planet below. Draal, an old friend of Delenn's, takes charge of the machinery in the planet, warning away all who would try to take it for themselves. The Mars rebellion is put down by Earth Alliance security forces.

In "Babylon Squared," Babylon 4 -- the biggest of the Babylon stations, which dissapeared 24 hours after coming online, suddenly reappears. Meanwhile, off-station, Delenn is chosen by the Grey Council to be their new leader, but declines because a Minbari prophecy tells her that her destiny lies on Babylon 5. She leaves with a powerful device called a triluminary. As time disturbances flash back and forward to other times (including a scene where something is coming through the walls of the station, being fought off by Garibaldi, as Sinclair is pushed into the crowds), the crew attempts to evacuate the crew of B4. A mysterious alien, Zathras, has appeared and tells of a great, terrible war, and the attempt to pull B4 through time to use it as a base of operations. He is looking for "The One" -- the great leader of an effort to bring peace to the galaxy. The station is evacuated, but Zathras, trapped, is rescued by "The One" -- who turns out to be a much older Sinclair, aided apparently by Delenn.

"The Quality of Mercy" reveals a clinic run by Dr. Franklin in the downbelow sections, as well as an alien healing machine that transfers "life force" from one person to another.

"Chrysalis," the season one finale, refers to the cocoon that Delenn begins to build using a mysterious crystalline machine. Garibaldi uncovers a plot to assassinate the Earth President, but is shot in the back by his right-hand man, left for dead. Morden reappears, and offers to take care of a problem for Londo, dealing with a region contested with the Narns. Delenn speaks to Ambassador Kosh, who reveals something to her that verifies her interpretation of a prophecy. She confronts Sinclair about his knowledge of his interrogation, but enters into her cocoon before they can talk. Londo is horrified to find that the Narn outpost has been utterly destroyed by mysterious forces. The president is assassinated, and the vice president is sworn in immediately. G'Kar leaves to investigate the destruction of the Narn base.