Sisko approaches Starfleet Command with Odo's suspicion that Gowron, the Klingon leader, is really one of Odo's people — a Changeling.

Sisko is then instructed to expose the Changeling. He is given four emitters that, when set up and activated around the Gowron impersonator, will force him to revert to his gelatinous state. The challenge is getting into Klingon territory while the warrior race is at war with the Federation — not to mention getting four individuals close enough to Gowron to expose him. Bashir solves this problem by surgically altering Sisko, Odo, and O'Brien to look like Klingons, while slightly altering Worf's appearance so he won't be recognized.

The foursome is taken into enemy territory on Gul Dukat's Klingon Bird-of-Prey, while Worf drills the group on Klingon behavior. Dukat also creates Klingon identities for the team and adds them to the list of candidates for the Order of the Bat'leth — an honor that will be bestowed by Gowron himself. The men plan to use their emitters on Gowron during the ceremony. Dukat's ship arrives at their destination, where he leaves Sisko, Odo, O'Brien, and Worf on their own.

The Klingons arrive at the Hall of Warriors, where the Ceremony of Commendation has begun. Sisko and the others blend in as best as they can until General Martok — Gowron's right-hand man — arrives, meaning Gowron won't be far behind. They hurry to set up their emitters, but Martok seemingly recognizes O'Brien, who is able to fool Martok into believing they fought side-by-side in battle. No sooner is O'Brien in the clear than a drunken Klingon bumps into Odo, causing him to drop his emitter. Another Klingon picks it up, demanding to know what it is. Worf hurries over and pretends the emitter is a prize from the battle. This is enough to send away the Klingon, just as Gowron enters the hall. Odo attempts to again set up his emitter, but a young Klingon has taken the designated spot. Acting every bit the warrior, Odo makes him move and finally accomplishes his task. Sisko is about to trigger the emitters when his name is called to accept his award. After he does, Sisko steps off the platform and prepares to finally activate the emitters. At that moment, he is knocked to the floor. Martok has recognized him and throws Sisko and the others into a cell.

In private, Martok admits to Sisko that he also suspects Gowron has been replaced by a Changeling. Since the emitters have been destroyed, he says Gowron must be killed in order to prove his identity, and leads the four back into the hall. But when Worf attacks Gowron, the Klingon leader insists on fighting one-on-one — behavior typical of a real Klingon. Martok wonders aloud why Sisko doesn't just shoot Gowron, and Odo realizes he has no concept of honor — meaning he must be the real Changeling — and exposes Martok. Everyone fires their weapons at Martok, who promptly turns into goo. Gowron realizes that the Founders misled Odo into thinking he was a spy so that the Federation would eliminate him and allow Martok to take control. But Gowron is still doubtful the war will end, since Klingons never turn back from battle. Still, he agrees to call a temporary cease-fire, and sees that Sisko and the others are delivered safely back to Deep Space Nine.