Threshold: Outbreak

With food supplies now infected with the alien DNA, the team tries to find the source of contamination before the outbreak becomes a population. Meanwhile, Lucas has an encounter with a Civil War-era human who somehow defeated the aliens back in the 1800's, and the only clue to how he accomplished this can be found in his journal. But Lucas doesn't know where to find it; and, Molly meets with an alien, who tells her that they have come to save human beings, as radiation from two collided neutron stars approaches Earth and will kill all life on it, unless human physiology is altered.