An alternate history in which Enterprise NX-01 was thrown back 117 years to 2037 by a subspace corridor and became a generational ship awaiting its younger self.
The displacement is revealed in the Enterprise episode E². As Archer prepares to use a subspace corridor to reach a meeting with Degra, a second, weathered Enterprise appears. Its captain, Lorian, explains that the corridor will hurl the ship back to 2037.
In that history the crew, unable to return and unwilling to change the past, stayed in the Expanse and raised families aboard, hoping their descendants could stop the Xindi. Lorian is the son of Trip Tucker and T'Pol, and an aged T'Pol still lives on his ship.
Lorian, haunted by an earlier failure to stop the probe sent against Earth, tries to steal Archer's plasma injectors, but the two crews end by working together. Archer's ship gets through the corridor safely. The older Enterprise then cannot be found, and its fate is unknown.