Season 4
Enterprise’s bold final season sees several multi-episode story arcs while establishing the foundation of what becomes the United Federation of Planets. The time-shattering season premiere concludes the Xindi arc, and the Temporal Cold War that has overshadowed the series since its premiere.
The season provides explanations to many disparities between this series and those past, including the Klingon appearance variation of the original series and the stark Vulcan cultural discrepancies.
As is common during the season, Enterprise crosses plots from previous Trek incarnations during its 3-part story arc involving fan favorite Brent Spiner guesting as Data creator Dr. Soong, who has created a genetically engineered clan of superhumans.
We revisit the mirror universe – first seen in the original series episode “Mirror, Mirror” and several times in Deep Space Nine – with a plot explaining how the alternated the universe evolved separately from our own.