DS9 Season 6 Episode 4 Behind the Lines

Plot

Returning from another mission against the Dominion on the Defiant, Captain Sisko is informed that Starfleet Intelligence has discovered a massive sensor array that the Dominion is using to track Starfleet ship movement. Sisko determines that the only way to destroy the array is to approach it from through a star cluster. However, Sisko is promoted to adjutant to Admiral Ross, and will not be commanding the mission. Commander Dax is placed in command of the Defiant. While Sisko misses his crew and frets over their safe return, Dax leads the mission and succeeds in destroying the array.
Meanwhile, Major Kira and the others on occupied Deep Space Nine are successful in spreading distrust between the Cardassians and Dominion, by allowing the Dominion's Jem'Hadar soldiers to find out about Cardassian officer Damar's proposal to poison the Jem'Hadar if supplies run out of the drug needed to control them. Meanwhile, the Cardassian leader Dukat has still not been able to destroy the Starfleet minefield preventing Dominion reinforcements from arriving from the Gamma Quadrant.
One of the Changelings, the shapeshifting rulers of the Dominion, visits DS9, hoping to spend time with Odo, a rogue Changeling who has lived among and allied with the Bajorans. She persuades Odo to "link" with her, physically joining their liquid bodies, so he can understand more about his people.
Damar, while drinking at Quark's bar, reveals that he has found a way to destroy the minefield by firing a beam from the station's deflector array. Quark relays this information to Kira, and she and Rom plan to sabotage the deflector. Odo offers to disable the security system so that Rom's interference goes undetected. However, when the moment comes, Odo is in the middle of linking with the other Changeling, and so when Rom begins his work, he sets off the security alarm and is captured by Damar. Kira confronts Odo, but he merely says that while linked nothing else matters.