Clusters of brain-dwelling parasites that exist in an interspatial flux outside normal space-time infect Captain Archer via a passing shock wave from a Delphic Expanse Sphere anomaly. Causing no tissue damage but impairing the formation of new long-term memories, the parasites in effect force Archer to relive each day with no knowledge of the event or passing time. Traditional therapies don't work, but after 10 years of research and consultation with Denobula's best neurosurgeons and quantum theorists, Dr. Phlox develops a highly focused anti-proton beam to attack the parasites; the only other alternative is a subspace implosion that would kill the patient as well. Phlox later realizes the parasites are non-linear when he removes the first cluster and all traces of them disappear from every prior scan of Archer's brain. When a Xindi attack leaves the surgical test chamber in ruin, Archer sacrifices the ship and himself in order to kill the parasites, trusting he will live again when the interphasic creatures' disappearance will in effect reset history.