I'll Give You the Grand Tour

Centuries before the present, a projectile strikes Viltrum and breaks into ten shards that seed a bioweapon tuned to attack Viltrumite genetics. The flashback lingers on the empire at its cruelest: slaves worked to death, children drilled to worship the late tyrant Argall, and a young Nolan surviving a brutal coming-of-age beating from his own parents. Then the sickness spreads. Citizens bleed from their eyes and mouths and drop where they stand, quarantines collapse, and the ruling regent orders every non-Viltrumite slave killed to smother any rumor of weakness. By the time it burns out, only about fifty of the race survive, and their dead are arranged into a memorial ring encircling the planet.

In the present, Nolan shares this history with Allen aboard a stolen ship bound for Talescria, admitting the empire's endless conquest was really a search for a species compatible enough to rebuild their numbers, which is why Earth and Mark mattered so much. After a tense reunion with Allen's partner Telia, the trio reports to Thaedus, who reveals himself as the first Viltrumite ever to turn against the empire. Nolan agrees only to recover dangerous weapons he once hid away, not to enlist in the coming war. Their salvage run across several worlds recovers the Infinity Ray, wins a wary promise from Space Racer, and gathers Sinlak Beetles whose shells can injure Viltrumites, though a reckless captain nearly gets everyone killed on the thawing homeworld of the Ragnars.

Thaedus finally exposes his darkest secret: he built and released the Scourge plague himself, making him responsible for the deaths Nolan just mourned, including his own family. Enraged, Nolan nearly strangles the old man, then relents. Thaedus, who keeps an improved strain ready as an absolute last resort, urges Nolan to face judgment for his own crimes. Shaken and unwilling to permit another genocide, Nolan accepts that more strength is needed and resolves to go back to Earth and ask Mark to join the fight. A closing scene shows the broken warrior Conquest kneeling before Grand Regent Thragg, who spares him because there is still work to be done.

The real cause of the Viltrumite decline is revealed to be a genetically targeted plague rather than simple attrition, paying off hints dropped across earlier seasons. Nolan learns Thaedus's identity as the empire's first defector and, worse, as the plague's architect. Space Racer is shown alive and willing to consider the Coalition, and the crew secures the Infinity Ray along with beetle-shell material for anti-Viltrumite weapons.

Thaedus holds a refined version of the Scourge virus as a final option, and Nolan forces a promise that it stays one. Nolan commits to recruiting Mark despite the bridges he burned on Earth. In the final beat, Thragg makes his first appearance, choosing to spare Conquest for his failure rather than execute him.

This is the only chapter in the series with no Grayson present at all, focusing entirely on Nolan and Allen as they gather resources for the final war. It marks the debut of Thragg, the strongest Viltrumite and Grand Regent, a moment originally slated for the previous finale's credits before time ran short. Space Racer, glimpsed only in a Season 2 flashback, appears in full for the first time, voiced by Winston Duke.

The episode dramatizes the Scourge event that earlier seasons repeatedly teased, showing the empire cut down to fewer than fifty survivors. Nolan wears a redesigned uniform, Allen's neural implant now supports group telepathy, and the story confirms that even Conquest is afraid of Thragg.