DS9 Season 7 Episode 6 Treachery, Faith, and the Great River

Plot

Odo is summoned to a secret rendezvous by Weyoun, who says that he has decided that the Dominion's war against the Federation is misguided, and offers to defect. Odo distrusts Weyoun, and is irritated that Weyoun considers him a god, but takes him into custody. Soon their runabout is hailed by another Weyoun, who explains that the Weyoun clone with Odo (Weyoun VI) was activated after the accidental death of the previous Weyoun; his successor, Weyoun VII, was activated when Weyoun VI abandoned his post and was deemed "defective". Weyoun VII orders Weyoun VI to activate his self-termination implant, but he refuses.
Damar persuades Weyoun VII to order the runabout destroyed to prevent Weyoun VI from reaching the Federation; Weyoun VII is reluctant to risk the death of Odo, a Changeling, but eventually consents. When one of his Changeling superiors demands an update, Weyoun VII is subservient but vague in his answers, not revealing Odo as their target. Damar notices that the Changeling looks unwell.
As they try to escape the pursuing Dominion ships, Weyoun VI reveals to Odo that an illness is spreading among the Changelings, with Odo possibly the only one uninfected. He urges Odo to be prepared to take command of the Dominion himself and turn it away from its imperialistic ways. Realizing they will be unable to escape, Weyoun VI tells Odo he lives to serve him, hails Weyoun VII, and triggers his termination implant. Weyoun VII immediately calls off the attack and allows Odo to escape. Before dying, Weyoun VI asks Odo for a blessing.
In a side plot on Deep Space Nine, Chief Miles O'Brien is missing a crucial piece of equipment needed to repair the starship Defiant. Nog offers to help O'Brien by navigating "the Great Material Continuum"—a Ferengi metaphor for the economics of supply and demand as a great river on which a skilled navigator can always find what he needs. O'Brien reluctantly authorizes Nog to make a long series of trades, including loaning out Captain Sisko's desk and selling a shipment of wine sent by General Martok's wife. An increasingly alarmed O'Brien watches with dismay as Nog works deal after deal while the required part appears no closer to arriving. In the end, the Defiant is finally repaired, Martok's wine is replaced with a better vintage, and Sisko's desk is returned before he even discovers it was gone.