“Rules of Acquisition” is episode seven of season two of Star Trek: Deep Space Nine.
A waiter in Quark’s bar, Pel, is proving to be surprisingly helpful and competent, but he isn’t what he seems – for he is actually a she. In Ferengi society, females are kept naked, are supposed to be submissive and silent, and can’t participate in business. Having one pretending to be a male is actually a criminal offence.
The Grand Nagus, Zek, also returns to the station (he had only faked his own death in “The Nagus”). He wants Quark to start expanding the Ferengi influence into the Gamma Quadrant by opening negotiations with one of the discovered cultures. The Nagus keeps making the negotiating status more and more difficult, and Pel is being increasingly useful – which is going to cause problems if she’s discovered. Which seems increasingly likely, as she’s become attracted to Quark.
This episode also sees the first mention of the Dominion – an element that will become increasingly important in the future.