An alternate history in which Archer's loss of memory let the Xindi destroy Earth, leaving a few thousand human survivors hiding on Ceti Alpha V until the timeline was erased.
This alternate history is shown in the Enterprise episode Twilight. In 2153 Archer is struck by an anomaly while saving T'Pol and infected with parasites from outside normal space-time, which stop him forming new long-term memories. He is relieved of command and T'Pol becomes captain.
Without him the mission fails. The Xindi weapon destroys Earth, and other human colonies are hunted down afterwards. About six thousand survivors settle on Ceti Alpha V, where T'Pol, having left Starfleet, cares for Archer for years.
Phlox at last finds that destroying the parasites also removes them from the past. As Xindi ships attack the convoy, Archer, T'Pol and Phlox set off a subspace implosion aboard Enterprise. The parasites are wiped out, and history resumes from the day of the accident with Archer well.