In a ceremony in the station's wardroom, Jake Sisko (Cirroc Lofton) pins a new pip on the collar of his father's, Commander Benjamin Sisko, uniform marking his promotion to the rank of Captain. Visiting Ambassador Krajensky then tells Sisko that a neighboring race, the Tzenkethi, may soon engage in war with the Federation. He says Sisko is ordered to bring the Defiant on a "saber-rattling" mission along the Tzenkethi border. Along the way, oddities occur on the ship and the crew suspects there may be a Changeling infiltrator. It is revealed to be Krajensky, but it is too late; he has already sabotaged the ship to the point it could instigate a war. After hours of searching, the crew tries to find the infiltrator with blood screenings but are unsuccessful. Sisko readies the ship's self-destruct while Chief O'Brien (Colm Meaney) tries to override the Changeling's systems. Constable Odo (René Auberjonois) fights the Changeling in main engineering and ends up killing him (becoming the first changeling to harm another). It is then revealed that Krajensky may have long been dead and this was a Dominion plot to destabilize the Alpha Quadrant. Back at Deep Space Nine, Odo reveals the cryptic message the Changeling said before he died: "You are too late. We are everywhere."