The Enterprise, under Captain Jonathan Archer, sets off on its maiden voyage with a mission to return a wounded Klingon to his people.

Starfleet orders Enterprise to return home when the crew seemingly causes the destruction of an alien planet. However, a visit from Crewman Daniels leads Archer to believe that this disaster was the plot of one of the factions from the temporal cold war.

Daniels and Archer must find a way back to the 22nd century in order to make sure history plays out as it should. Meanwhile, on board Enterprise, the Suliban have taken over the ship, but Reed, Trip, and T'Pol formulate a plan to eject the aliens.

An alien race known as the Xindi launch an attack on Earth, causing great casualties and massive damage. As Enterprise heads back home, an unlikely source informs Archer about the Xindi and that their next attack will destroy Earth.