I will have to disagree with Rimrod's assessment of the religious plot of this episode. Passing through Gethsemane is perhaps the most powerful episode of Babylon 5 I have watched, and the religious nature of the plot is neither tacked on nor overblown, but instead dovetails with the entire arc of the series.
The conventional division of Babylon 5 episodes is into two categories: arc and non-arc. This episode is non-arc, meaning that the main plot does not move the overall story of the series forward. However, as with other non-arc episodes such as Believers, The Quality of Mercy, or Confessions and Lamentations, this episode is meant to reflect on the issues of the story arc in a more personal way.
Although it can be phrased different ways, the basic philosophical grounds of Babylon 5 are to investigate the polarities between mercy and judgment, chaos and order, identity and sacrifice, as evidenced by the Shadows and the Vorlon. (And, if you want to phrase it this way, Chesed and Geburah.) This episode demonstrates these same issues, but on a much more intimate level.
The plot centers around Brother Edward, one of Brother Theodore's monks. Brother Edward is in every way shape or form a conscientious, self-sacrificing monk whose biggest self-doubt is whether he would have the ability that Jesus showed at Gethsemane, to wait and accept the need to sacrifice himself. In a brief but powerful series of images, it is revealed that Edward might have a hidden past, and in uncovering his past, Edward receives the knowledge that lets him see why sacrifice can be desirable. And after that, there is a twist, in Twilight Zone manner, that makes the line between forgiveness and judgment even more unclear, and the thin line between them even more ironic.
So in all, a multilayered, well-executed story that has a deep bearing on the storyline as a whole.