Archer, T'Pol and Trip land at a deuterium mining colony to trade for some of the isotope. Tessic, the head of the facility, is unpleasant and tells them to come back another time... the deuterium they have stored is for someone else. Archer manages to cajole the miners into trading a small amount of deuterium for some power cells and medical supplies.
Turns out, the previous customers are a band of Klingons who are simply taking what they want (i.e. all the deuterium) and leaving just scraps for the colonists to survive on. Tessic tells the Klingon commander, Korok, that they can't meet quota. Korok is angry at the shortage, and will be back in four days for the full supply.
Tessic gives Archer his small amount of deuterium just to make him leave. It isn't enough for Archer... he plans to teach them how to fight this small band of Klingons. The Enterprise crew teaches basic hand-to-hand survival combat as well as small arms training. When the Klingons return, the face unexpected resistance, and fall into Archer's trap -- he's moved the camp slightly so that the deuterium wells can be used to ensnare the Klingons -- who leave in a huff, vowing that they can get their deuterium someplace else. In thanks, the colonists give Enterprise ten-times more deuterium than their originally agreed upon amount.