Plot summary
The Federation plans to deliver several replicators through Deep Space Nine to Cardassia following attacks by the Klingons that debilitated the Cardassian industrial base. Eddington briefs DS9's command staff that Starfleet fears that the shipment will be intercepted by the Maquis. Eddington and Security Chief Odo warn Captain Sisko that they believe his girlfriend, Kasidy Yates, is working with the Maquis. Sisko is reluctant to believe them, but after Yates refuses to allow her cargo to be inspected, he instructs Lieutenant Commander Worf to follow Yates' ship, the Xhosa, in the Defiant. Worf confirms that the Xhosa delivered supplies to a Maquis ship in a region of space known as the Badlands.
Eddington tells Sisko he is unwilling to take responsibility for arresting Yates, so Sisko takes command of the Defiant to follow the Xhosa to its next rendezvous with the Maquis. When no Maquis ship arrives, Odo suggests this operation might have been a ruse to lure Sisko away from Deep Space Nine. Sisko confronts Yates on the Xhosa. She claims she has only been delivering medical supplies to the Maquis, and was told that today's delivery was urgent. Fearing deception, Sisko lets Yates go and sets course back to Deep Space Nine.
Meanwhile, in Sisko's absence, Eddington orders Deep Space Nine's security crew to transfer the replicators to a waiting ship. After rendering second-in-command Major Kira unconscious, he removes his badge and flees the station. When Sisko returns, Eddington contacts him to acknowledge his defection to the Maquis and promise further trouble if the Federation aids the Cardassians. Sisko vows to capture and arrest Eddington himself. Later, Yates returns to the station alone, having left her crew in the Badlands, to turn herself in. Sisko and Yates have an emotional embrace before she is taken to the brig.
In a side plot, Tora Ziyal, the half-Bajoran daughter of the former Cardassian prefect of Bajor, Gul Dukat, attempts to befriend the exiled Cardassian spy-turned-tailor Elim Garak. Garak fears that Ziyal has been instructed to kill him, since Garak was responsible for the torture and death of Dukat's father years ago. Ultimately she persuades Garak that she is merely interested in being his friend, as the only other Cardassian on Deep Space Nine.
Credits
Adapted from Wikipedia contributors, For the Cause (Star Trek: Deep Space Nine). Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.