巴比伦5号 第四季

In 2261, the Vorlons entered the Shadow War, but their methods soon caused alarm among the alliance. They began annihilating entire worlds they believed to be "tainted" by the Shadows, sparking a controversy. Disturbed by this sudden turn of events, Babylon 5 enrolled the assistance of several other powerful and ancient races, known as the First Ones, to unite against both the Shadows and the Vorlons. Captain John Sheridan returned to the station after escaping Z'ha'dum, but at a heavy cost: he was informed that he had but 20 years left, barring illness or injury. Accompanying him was a mysterious alien named Lorien, who claimed to be the oldest sentient being in the galaxy.

Just hours before Sheridan's arrival, Garibaldi was retrieved from a precarious situation and returned to the station. His demeanor was distinctly more paranoid and skeptical of alien races and Sheridan than before.

Centauri Emperor Cartagia established a partnership with the Shadows. Londo Mollari masterminded Cartagia's assassination and renounced his alliance with the Shadows. He killed Mr. Morden and destroyed the Shadow vessels based on the Centauri homeworld, endeavoring to save his planet from the Vorlons' impending destruction. With the support of other ancient and several younger races, Sheridan lured both the Vorlons and the Shadows into a colossal battle. In the fray, the Vorlons and Shadows disclosed that they had been designated as guardians of the younger races, yet due to philosophical discrepancies, they had ultimately become pawns in their age-old wars. The younger races rejected their ongoing interference, and the Vorlons, the Shadows, and the remaining First Ones agreed to depart the galaxy permanently.

Following the Shadows' defeat, Garibaldi resigned his post as security chief and embarked on his own as an "information provider." He began collaborating with William Edgars, a Martian magnate married to Garibaldi's former paramour. As his ties with Edgars grew stronger, he became progressively adversarial towards Sheridan and ultimately left Babylon 5.

Minbar was ensnared by a brief civil war between the Warrior and Religious factions. Delenn clandestinely met with Neroon of the Warrior caste and convinced him that neither side should emerge victorious. She told him she was prepared to undergo a ritual of self-sacrifice, but would abort it just before death. When Neroon witnessed her sincere intention to complete the ritual, he saved her, sacrificing himself in her place, and declared that, although he was born as a Warrior, in his essence, he was Religious.

As part of the ongoing conflict between Earth and Babylon 5, Garibaldi betrayed Sheridan, arranging his capture to gain Edgars' trust and uncover his plans. Garibaldi later learned that Edgars had created a virus hazardous only to telepaths. It was then revealed that Garibaldi had actually been abducted by the Psi-Corps at the end of Season 3, re-programmed by Bester to provide information at strategic moments. Bester released Garibaldi from his programming, allowing him to recall all his actions since his abduction. Edgars was eliminated, and his wife vanished, only to reunite with Garibaldi after the war's end. Garibaldi aided in freeing Sheridan and returned him to the fight for Earth's liberation. A Babylon 5-led alliance freed Earth from President Clark's totalitarian regime in a brief yet violent conflict. This led to Clark's suicide and the restoration of democratic governance. Mars was granted full independence, and Sheridan agreed to resign his commission. The League of Non-Aligned Worlds was dissolved and restructured into the Interstellar Alliance, with Sheridan elected as its first President and continuing to lead the Rangers, akin to United Nations peacekeepers.

In the season finale, the narrative expanded to depict the long-term impacts of Babylon 5's legacy 100, 500, 1000, and one million years into the future, showcasing its enduring influence throughout history. The events portrayed included the political repercussions of the 2261 civil war, a subsequent nuclear war on Earth involving a new totalitarian government in the year AD 2762, Earth's descent into a pre-industrial society as a result, the loss and eventual rediscovery of humanity's knowledge of space travel, and the final evolution of mankind into energy beings akin to the Vorlons before Earth's sun went nova.