In "War Without End, Part 1," Captain Sinclair unexpectedly returns to Babylon 5 and assembles a team, including Sheridan, Delenn, Marcus, and the enigmatic Zathras, for a secret mission to Sector 14. This mission involves helping ancient warriors of light in a past conflict while avoiding making changes to the future. The episode introduces a complex mystery involving time travel, the fate of Babylon 4, a spectral figure in a spacesuit, and the question of a prophesied "One," all of which threaten to alter the timeline and potentially lead to a Shadow victory.