Twilight

While saving T'Pol from a spatial anomaly, Archer is infected by parasites that leave him unable to form new long-term memories. He remembers everything before the accident, but new memories fade within hours. With Archer unfit for command, T'Pol takes over, but the mission fails: the Xindi destroy Earth, and the surviving humans flee in a convoy, eventually settling on Ceti Alpha V. T'Pol gives up her career to care for Archer. Twelve years later Phlox arrives with a possible cure, and finds that removing the parasites erases them from earlier scans too, meaning Archer might never have been infected at all, and Earth might be saved. Before the treatment is complete, the Xindi attack. Captain Tucker and the bridge crew are killed, and Archer, T'Pol and Phlox trigger a subspace implosion that destroys both the parasites and the Enterprise. Time resets, and Archer recovers from his injury with his memory intact.