Babylon 5 is swamped with Narn and other war refugees passing through. By order of Captain Sheridan, any too sick or injured to travel are sent to medbay until they are well enough to travel. Sheridan holds Morden in custody and learns some of what happened to the expedition on which his wife was lost. Kosh and Delenn explain to Sheridan about the Shadows. Kosh warns Sheridan "If you go to Za'Ha'Dum, you will die." The Night Watch is introduced as a vigilance Organization.
I'd like to live just long enough to be there when they cut off your head and stick it on a pike as a warning to the next ten generations that some favors come with too high a price. I would look up at your lifeless eyes and wave like this. Can you and your associates arrange that for me, Mr. Morden?
The history of the war between the Shadows and the other races, including the First Ones, is described for the first time.
This episode was originally intended to air after "Knives", rather than before, with Sheridan's hallucination of the Icarus in that episode serving as a reminder to the audience of his wife's fate before more details were revealed in this episode.
The name Z'ha'dum can be seen as a homage to Tolkien's Khazad-dûm (Moria) in Middle Earth. Just as Khazad-dûm has been abandoned for many years, and is now inhabited by an ancient evil, so too Z'ha'dum, once the home of a mighty civilization, is now the home of an ancient and deadly evil.