Season synopsis
Contains spoilers for this season and earlier seasons.
Enterprise begins the year stranded in an altered 1940s, where alien operative Vosk has used time travel to help Nazi Germany control the northeastern United States. Archer works with Silik and resistance fighter Alicia Travers to stop Vosk’s scheme; the crew disrupts the temporal device, restores the timeline, and ends the Temporal Cold War. Back on Earth, Enterprise is welcomed home after the Xindi crisis, but Phlox faces hostility during shore leave and T’Pol must consider her arranged marriage to Koss. Tucker and T’Pol’s relationship continues through these personal and political changes.
Archer and T’Pol help expose a Vulcan political conspiracy and recover the Kir’Shara, an artifact that prompts a shift toward Surak’s teachings. An Andorian–Romulan crisis then forces Archer and Shran to bring Andorians and Tellarites together against a remote-controlled Romulan ship. Later, Enterprise and Columbia investigate a Klingon illness linked to genetic engineering. These encounters draw the crew into the disputes between neighboring powers, with cooperation repeatedly depending on whether old enemies can work together against a shared threat.
The main story closes with “Demons” and “Terra Prime”: xenophobic leader John Frederick Paxton threatens Starfleet Command from Mars unless aliens leave Earth. Archer’s team stops his weapon, and Archer urges delegates at the interspecies conference to explore space together. The episode also reveals that T’Pol and Tucker’s genetically engineered daughter, Elizabeth, is gravely ill; Phlox cannot save her, and the baby dies. The last episode then jumps six years ahead to 2161, framed as William Riker’s holodeck recreation. During the Federation Charter ceremony preparations, Shran asks Archer to rescue his kidnapped daughter; Trip dies protecting Archer, and Archer enters the hall to give his founding speech.