With Enterprise's deuterium reserves running low, Archer and the crew visit a small mining colony in hopes of replenishing their supply. The alien colonists, however, claim that they can't spare any deuterium, and ask Archer to return at the end of the season. Archer manages to negotiate, and eventually reaches an agreement with the colony's leader, Tessic — the deuterium in exchange for medical supplies, power cells and assistance in repairing the colony's extraction pumps. In a puzzling move, Tessic also insists that the pump be repaired within two days.
As the Enterprise crew is helping with repairs, a Klingon ship enters orbit. Tessic panics, insisting that Archer and his people hide. As Archer watches, a small group of Klingons beams to the surface, greeting Tessic in what appears to be a friendly manner. The leader of the Klingons, Korok, is significantly less friendly when he learns that Tessic does not have the deuterium he has requested. Tessic asks for more time to produce it, but Korok becomes enraged, and orders Tessic to have the deuterium ready in four days. Finally, the reason for the colonists' strange behavior becomes clear — these Klingon marauders have been preying on them for five seasons, taking all the first-yield deuterium they can produce. When Tessic and the others tried to rebel, it resulted in the deaths of eight colonists. Defeated, Tessic tells Archer to just take the deuterium he needs and leave.
Archer, however, is angered by the situation, and believes that the crew of Enterprise may be able to aid the colonists. He convinces Tessic to allow them to try, and reveals a plan: the colonists will surreptitiously move their village and rigs so that when the Klingons arrive for their next visit, they will be lured into a combustible fuel field. To protect them in battle, T'Pol offers some rudimentary self-defense training, while Reed and Hoshi lead the colonists in target practice.
When the Klingons do arrive, Archer's scheme is a success — the colonists defend themselves against the marauders, and the Klingons are tricked into entering an area that appears to be barren desert. This "desert," however, is the deuterium field, and flaming deuterium explodes from the wellheads surrounding them. As the Klingons are surrounded by a ring of fire, Tessic approaches, warning the Klingons to leave and never return. Rattled, Korok and his crew beam back to their ship.
As Archer and his crew prepare to leave, a grateful Tessic gifts them with 2,000 liters of deuterium — significantly more than the initially agreed upon amount.