Season synopsis
Contains spoilers for this season and earlier seasons.
With Archer stranded in the 31st century after “Shockwave,” the Suliban take Enterprise and its crew to their helix. Tucker and the officers coordinate an escape, Archer finds a way back, and together they expose the Suliban’s role in the Paraagan disaster. Starfleet allows the mission to continue, leaving the Temporal Cold War active while the ship resumes exploration. The crew also meets new powers, including the Romulans and Borg, and its encounters with Andorians and Vulcans deepen the political strains first seen in the previous season.
Many stories follow separate assignments: Enterprise is repaired by an unmanned station after a cloaked mine damages the ship; Archer negotiates a ceasefire between Andorians and Vulcans; and the crew finds Borg survivors in Arctic ice. T'Pol is reactivated as a Vulcan intelligence agent and later learns she has Pa'nar Syndrome, contracted during a mind meld; she faces ostracism from Vulcan society. These events keep the ship's contacts with nearby powers unpredictable as the crew continues its deep-space mission.
That changes in the finale, when an alien probe cuts a destructive path across Earth, killing millions, including Tucker’s sister Elizabeth. Archer learns that the Xindi launched the attack after being manipulated by a faction in the Temporal Cold War that warned them humans would destroy them in the future. Starfleet refits Enterprise with stronger weapons and assigns MACO soldiers for a pursuit into the dangerous Delphic Expanse. T’Pol resigns her Vulcan post to remain with the crew, and the NX-01 sets out to stop a second strike, leaving the Xindi threat unresolved for Season 3.