The crew finds a pre-warp society and a hidden alien.
Enterprise finds a planet whose people, the Akaali, are at roughly a pre-industrial stage, but sensors detect a power source far too advanced for the society. Archer, T'Pol, Sato and Tucker beam down in disguise to investigate.
They discover that an alien group, the Malurians, are secretly mining the area and poisoning the local water supply, making the Akaali sick. Archer gains the trust of an apothecary named Riaan, who has been studying the illness, and he works to stop the Malurian operation without revealing to the Akaali who the humans really are. The episode was directed by Mike Vejar and written by Mike Sussman and Phyllis Strong.