The crew had gotten a message from their future, Sinclair came back to the station, they all took off, sans Garibaldi to Sector 14 because they were the ones who stole Babylon 4, but in the process, Sheridan was lost in the timestream, where he finds himself facing an irate Emperor Mollari. Londo shows him the devastation wrought on Centauri Prime, fallout from the war 17 years ago. He has the guards take Sheridan away, warning him to make peace with whatever gods he believed in.
As he paces in his cell, he suddenly starts getting pulled into the timestream again, where Zathras sees him. As he settles back in the future, the Delenn of that time is thrown in. She comes over and hugs him, telling him she didnt tell them anything, that she isnt afraid, their son is safe, and that she loves him before kissing him. Clearly quite a bit has happened in seventeen years.
The rest of the crew are on Babylon 4 to arrange for its move through time. They manage to clear out one section of the station to give them space to work.
In the future, Sheridan interrupts Delenn and tells him what he remembered last. She remembers him telling her about this years ago, and gives him dire warnings about some of the things they go through before the Centauri come for them. They are marched back to the throne room to find Londo nearly passed out. He is just coherent enough to tell them that hes being controlled by a creature attached to his neck, but he can put it to sleep with enough drink for a while. They have until it wakes up to escape with a ship hes made available for them. As they leave GKar comes in and Londo says his keeper will awaken soon and warn "the others" of the escape.
- Londo: We have unfinished business between us, GKar. Let us make an end of it, quickly. Before it stops me. I am as tired of my life as you are.
GKar grabs Londos neck and begins squeezing, but the Keeper awakens and forces Londo to retaliate. Meanwhile, Sheridan begins slipping into time again. Delenn gives him some advice before he goes.
- Delenn: Treasure the moments you have, savor them for as long as you can, for they will never come again. John, listen to me: do not go to ZHaDum! Do you understand? Do not go to ZHaDum!
As Sheridan slips away, Vir comes into the throne room, finding Londo and GKars dead bodies and picks up the Seal of the Centauri Republic, thereby becoming emperor.
Zathras has devised a means to keep Sheridan there if he reappears, but Marcus and Ivanova are skeptical. They talk a bit about the time theyre going to, and how Valen emerged from that time. She wonders if theyll get a chance to meet him, but theyre interrupted when Sheridan appears again.
- Zathras: Nobody listens. Quite mad, they say. It is good that Zathras does not mind; he has even come to like it.
Sheridan asks for a status update, and they tell him they can proceed. He and Sinclair head to attach the beacon to the power core. Zathras warns that it is very delicate, but Major Kranz, fearing a hostile presence, pumps up the power levels, accidentally activating the beacon, and moving them through time, four years ahead, exactly when B4 showed up last time. Ivanova tries to get a hold of Sheridan but Sinclair says hes gone again, and theres another problem.
The stations staff are having problems of their own and, believing theyre about to explode, manage to convince Major Kranz to evacuate. As he orders a signal sent out, another tachyon burst erupts. Delenn flashes forward and sees herself in Sheridans quarters looking over a snowglobe when the door opens and a womans voice says, Hello. Delenn is so stunned she drops it.
The flash ends and, but theres no time to make sense of it; Sinclair arrives considerably aged, an effect of entering the tachyon field unprotected last time, and why he didnt want Michael along. Theres no time to worry about that, they still need to get the job done, and they need to get Sheridans stabilizer fixed before they lose him for good. Zathras thinks he can fix, but he needs tools. Sinclair will go try and keep the beacon stable.
As Marcus monitors the readings, they pick up the shuttle flight Sinclair led to Babylon 4 two years ago.
Meanwhile, Zathras manages to get the time stabilizer fixed, but is found by station security. Ivanova reports the situation, and says she going to try and reach C&C to have more direct control, while Kranz explains the situation to Past!Sinclair and Garibaldi, including Zathras.
Delenn, meanwhile runs off and is able to find Sheridan as he reappears again. In C&C, the lieutenant orders everyone out, and Ivanova manages to sneak in. As Zathras explains whats happening someone calls for the major, saying, "It's back!" He, Sinclair and Garibaldi rush out to see a figure in a blue space suit fading in and out. Zathras follows and says, "It is the One!"
Ivanova manages to get control and warns Sinclair off.
Past!Sinclair reaches out to the figure, but when they touch he is knocked back. Zathras then rushes over to the One, and hands over the time stabilizer. The One vanishes and Zathras tries to escape but is captured again. He warns them that they are finished and must leave or be trapped there forever.
Back near the White Star, Marcus finds Sheridan and rushes over to help. He realizes someone switched time stabilizers with him, since the one he has wasnt damaged.
- Marcus: But if youre here, who's running around out there in a blue suit?
The answer comes when Zathras is pinned under a support beam, and finds The One standing over him, removing the suits's helmet to reveal Delenn.
Sinclair comes back after trying to contact Garibaldi and warn him of the impending betrayal, but the shuttle was already out of range, a fact he laments to Delenn.
In C&C, they make final preparations, and Sinclair tells them to go back to the White Star, but Marcus stops him. He figured out that someone will need to go back with the station, and Sinclair admits hes right, but that hes still the one who needs to go, because he told himself in a letter he wrote 900 years ago. The others arent happy but eventually agree to let him go, besides, the aging effect will probably kill him if he doesnt.
Before they go, Zathras shares some words with Sinclair, Sheridan and Delenn about what he's learned.
- Zathras: Zathras has studied the great machine, knows things even Draal does not know yet. And I know you [Sinclair]. And I know you [Delenn]. And I know you [Sheridan]. All Minbari belief is around three. Three castes, worker, warrior, religious. Three languages, Light, Dark, Grey. The Nine of the Grey Council, three times three. All is three. As you are three. As you are one. As you are the One. You [Sinclair] are the One Who Was. You [Delenn] are the One Who Is. You [Sheridan] are the One Who Will Be. You are the beginning of the story, and the middle of the story, and the end of the story... that creates the next great story. Ah, in your heart, you know what Zathras says is true. Go now, Zathras' place is with the One Who Was. We have a destiny.
Sheridan and Delenn bid Sinclair their farewells and slowly leave.
As the White Star emerges from the temporal rift, the crew discuss what happened, and Delenn reveals that something happened a thousand years ago to cause human and Minbari souls to start merging. Her change was partly to restore balance between them. If the ancient Minbari had found Babylon 4 with a human aboard, they would never have accepted it.
During the transition, Sinclair uses a triluminary to enter a chrysalis similar to Delenns and become a Minbari, and as the ancient Minbari come aboard he introduces himself to them as Valen.
This episode contains examples of:
- All There in the Manual: The events at the future Centauri Prime are expanded upon in the canonical The Legions of Fire trilogy.
- Bad Future: The fate of Centauri Prime.
- Because Destiny Says So: Sinclair must take Babylon 4 back in time because he always has and always will.
- Bill... Bill... Junk... Bill...: Zathras searching for the right tools to fix the time stabilizer with. "No... no... never use this...."
- Vir picking up the Seal of the Centauri Republic and thus assuming the throne fulfills Lady Morella's prophecy.
- Londo and G'Kar end up choking each other to death.
- A Sinclair travels back in time, he remembers things the Soul Hunter told him ("They're using you!"), and his conversation with Neroon ("You talk like a Minbari, Commander.").
- The Chosen One: Three of them: The One Who Was (Sinclair), The One Who Is (Delenn), and The One Who Will Be (Sheridan).
- Crazy Enough to Work: So we're going to use Time Travel to steal a space station, then take it 1,000 years back in time to fight a war that will save the present day from being overwhelmed? Stop explaining, let's just do it.
- The Emperor: Londo, then Vir.
- Eyepatch After Time Skip: G'Kar.
- Zathras mentions Delenn and Sheridan as "The One Who Is" and "The One Who Will Be" respectively. Shortly after, Delenn becomes the new Ranger One, a position Sheridan is shown to have at the time of his death twenty years from now.
- Delenn also has a vision of herself watching Sheridan sleep when the door opens and a woman's voice says, "Hello."
- When it turns out that Sheridan and Delenn are Married in the Future.
- In Vino Veritas: Londo drinks himself into a stupor, because it is the only way to act freely without his Keeper interfering.
- Luck-Based Search Technique: Marcus happens to knock off the access panel Ivanova is looking for with his fighting pike. This after he'd said he didn't believe in luck.Marcus: Then again....
- Mutual Kill: Londo has G'Kar strangle him to keep his keeper from sending an alert of Sheridan and Delenn's escape, but it wakes up and forces him to respond, resulting in both their deaths.
- Nothing Is the Same Anymore: The heroes can now no longer rely on Valen's prophecies, as Sinclair wasn't around to see what happened after this.
- Obfuscating Stupidity: If it wasn't clear before, it's clear now that quite a bit that Zathras said in "Babylon Squared" was not truthful, or deliberately masking the truth. For example, he knew full well when in time the station was meant to go, but passed it off at the time as "Mathematics not Zathras' skill." He also lied about not having a time stabilizer. Quite a bit of truth was mixed in with the lies, though.
- On Second Thought: Marcus upon being Instantly Proven Wrong after declaring he doesn't believe in luck.
- Prepare to Die: Before Sheridan is taken to a cell, Londo tells him, "Make peace with whatever gods you worship. You will met them the next time I send for you."
- Previously On : Jeffrey Sinclair gets this one.
- Properly Paranoid: Major Krantz, which is understandable given that the previous three Babylon stations were sabotaged and they just saw a nuclear bomb go off.
- Prophecies Are Always Right: Lady Morella prophecies that both Londo and Vir would be emperor, one after the other is dead. Londo dies here and Vir succeeds him.
- Rapid Aging: Sinclair, as a result of unprotected exposure to tachyons on Babylon 4 before.
- Restricted Rescue Operation: Sinclair is unable to do anything to stop the Earth-Minbari war from happening as it could disrupt the Stable Time Loop and give the Shadows an advantage.
- Rule of Three: The three of The One, the One Who Was, the One Who Is, and the One Who Will Be.
- Spanner in the Works: Major Krantz causes several problems, including the original disappearance of the station while trying to locate and apprehend the intruders.
- Stable Time Loop:
- Sinclair goes back in time aboard Babylon 4 and becomes the Minbari leader Valen. At the end of his life, writes letters to himself and Delenn telling them what needs to happen. Not only that, the Triluminary itself is sent back, to be "created" by Valen... meaning that the object itself now has no actual origin.
- The disappearance and reappearance of the station itself. The crew were trying to get the construction crews to evacuate, but Major Krantz inadvertently causes the disappearance in response.
- Word of God is that the Triluminary wasn't the same one given to Delenn; the one Sinclair used was in the items that Zathras brought up from Epsilon III. Furthermore, it's been mentioned before (in a throwaway line in Babylon Squared) that there are three Triluminaries, not just the one we've seen—presumably, all three were brought by Valen. So, while certain parts of the loop fit the no-origin paradox (Sinclair writing to his younger self in the future being a major one), the Triluminary isn't one of them.
- Transformation Trinket: The Triluminary Sinclair uses to enter a chrysalis similar to the one that changed Delenn.
- Write Back to the Future: Where the letters came from, Sinclar as Valen wrote them 900 years ago.