Sisko is promoted to Captain. Ambassador Krajensky briefs the command personnel on a coup d'état within one of the Federation's newer allies, the Tzenkethi, a former enemy. He recommends that they dispatch the Defiant as a show of Federation strength to ensure that the new government does not break the treaty. As they near Tzenkethi space, they realize that they have been tricked and that the Defiant is now under the control of a Changeling who is determined to start a war.

Lawrence Pressman (Ambassador Krajensky)
Kenneth Marshall (Lt. Cmdr. Michael Eddington)
Jeff Austin (Bolian)

• This is the first episode to show the Defiant's engine room.
  
• Odo is forced to kill the changeling in this episode, and becomes the first changeling to ever harm another.