Season synopsis
Contains spoilers for this season and earlier seasons.
After the Xindi probe devastates Earth, Enterprise enters the Delphic Expanse on a mission to find the makers of the weapon and prevent another attack. A MACO unit joins the crew, and Captain Archer follows clues through the region’s dangerous spatial distortions while learning that the Xindi are not a single united people. The crew traces weapons materials to the construction effort and encounters the five Xindi species, whose council is divided over whether Earth should be destroyed. T’Pol and Tucker carry much of the strain as the mission grows more dangerous and Archer’s decisions become harder.
In “Azati Prime,” Archer attempts a one-person attack on the weapon, but finds it has been moved and is captured. Before the mission, Daniels shows him a future battle in which the Federation defeats the Sphere Builders, explaining why they want to prevent its formation. Archer uses that evidence to appeal to the Xindi scientist Degra. Enterprise is heavily damaged in the ensuing attack, and T’Pol struggles with command. As divisions widen within the Xindi council, Archer works to gain allies against the Reptilians who remain committed to destroying Earth.
Enterprise’s crew and its Xindi allies ultimately destroy the sphere network, ending the Expanse’s distortions, while Archer and his team destroy the weapon near Earth before it can fire. Archer is left behind and presumed dead, but the crew returns home and believes the immediate attack has been stopped. On arrival, however, they find themselves in an altered Second World War, with alien forces allied to Nazi Germany. Elsewhere, Archer is alive in a German field hospital, where an alien in an SS uniform emerges from the shadows.