The Terran Empire Seizes the USS Defiant

In the mirror universe, humanity did not greet the Vulcans in peace in 2063: Cochrane's followers killed them and seized their ship, founding the brutal Terran Empire. In 2155 the ISS Enterprise, under Captain Maxwell Forrest, learned that the Tholians had pulled a starship from another universe and another era into their space through an interphase rift.

The ship was the USS Defiant, a Constitution-class Starfleet vessel from 2268 in the prime universe, lost in a Tholian trap. Commander Jonathan Archer took over the mission in a mutiny, captured the Defiant and fought off a Gorn saboteur on board. Dazzled by a ship a century ahead of anything the Empire had, he dreamed of using it to make himself emperor.

His ambition was short-lived: his lover Hoshi Sato poisoned him and proclaimed herself empress from the Defiant's bridge. The episode shows that the borders between universes are porous, and that the Defiant's records gave the Terrans a glimpse of the Federation of the prime universe.