This is one of my favourite episodes in terms of the writing, because the three plots are linked and work well together (unlike the disaster to come that is TKO).
A close friend of Ambassador Delenn's, Minbari poet Shaal Mayan, is visiting the station. On her way back from Delenn's quarters she's attacked by an Earth-First hate group, who leave her stabbed and branded. This isn't the first attack, and although Commander Sinclair puts security chief Garibaldi on it, it's not enough for Ambassador G'Kar who starts agitating the alien population to fight back. This always strikes me as out of character for G'Kar, making a public spectacle being more Ambassador Mollari's sort of thing. While the show hasn't yet revealed anything about his past as a freedom fighter, he's been shown to be a private person who deals with problems behind the scenes - as he did when there was a price on his head. Inciting to riot doesn't seem like his style.
In the meantime, a pair of Centauri runaways arrive on the station, Kiron and Aria, who've been betrothed to other people but want to marry each other. They end up in Mollari's custody, in part because Kiron is his aide Vir's cousin. Mollari is less than sympathetic - marrying for love is just not done in Centauri society. He himself has three wives, who he refers to as pestilence, famine, and death (fittingly placing himself as war) although none of them are on the station with him. He books Kiron and Aria passage home and washes his hands of the matter.
Ivanova also receives a visitor, an old boyfriend Malcolm Biggs. For a while it looks like he wants to rekindle their relationship, but it soon turns out he has other motives. When Kiron and Aria are hospitalised by the same group that attacked Mayan, there are retaliatory attacks on humans - one a known xenophobe who was questioned about the previous attack. Biggs is caught on camera trying to recruit him into the Home Guard, an Earth-first terrorist faction.
Sinclair engages in skullduggery. He recruits Ivanova to plant some seeds about how he's unhappy with aliens on Earth himself, and introduce them. Sinclair's rude to the ambassadors at a reception, and in short order is telling Biggs how he "really" feels. Biggs takes the bait and is arrested along with his accomplices who attacked Maya, Kiron, and Aria.
Not only do the plots tie together well, but there's some nice characterisation. We hear from Biggs how Ivanova always put her career and duty before her personal life, and then we see it in action - firstly when she cuts her conversations with him short because of problems on the station, and later when she agrees to help Sinclair take him down. There's more of the Minbari as a deeply spiritual people, shown in Delenn's relationship with Mayan and Mayan's reaction to being attacked, and this in turn influences how Mollari decides to deal with his young runaways.
Mayan tells him he should allow Aria to sit in Medlab with Kiron while he's unconscious, because love is a potent healing force. Mollari, with his three unloved and unloving wives, is initially scathing - young people should learn to live without love. "As you did?" she asks him. It's only been a few episodes since Mollari was revealed to be a romantic himself, and a large chunk of future plot hinges on his inability to live without the one he loves. In the end, he arranges for Kiron and Aria to be fostered by his second cousin, which will bring honour to their own families, and when they're old enough will be allowed to choose for themselves who to marry.
There's also a tiny bit of the main story arc, with just enough Ambassador Kosh to be funny without his deliberate vagueness becoming annoying. Garibaldi and Sinclair muse about the nature of Vorlons, and remind the audience of the events of the pilot- of how Kosh was poisoned despite being in his encounter suit, and how the doctor and telepath who were the only people to respectively see and scan a Vorlon were shipped back home shortly after. This is the only part of the episode out of place, since it doesn't tie into the episode other then Sinclair using the attacks as an excuse to talk to Kosh. It's more moving pieces into place than movement, but those pieces will be important later.