Worf prepares to accompany Jadzia Dax and Kor, a legendary Klingon warrior, on a mission to recover the Sword of Kahless, the mythical, millennium-old weapon of the Klingon Empire's first leader – an artifact missing for centuries. When the drunken Kor finally retires to his quarters after first speaking with Worf, he is attacked by a Lethean, who reads his mind, then erases the incident from Kor's mind. Kor is crestfallen.
The next day, Captain Sisko – hoping to restore Federation/Klingon relations – allows them the use of a runabout for travel to the Gamma Quadrant world where the sword is believed to be located. Upon arrival, the three get into a deserted, protected chamber, but find that all the artifacts hidden there have been removed. But Worf, unwilling to give up, discovers another hidden chamber, where they finally find the Sword of Kahless. Later, Worf decides that it is his destiny, not Kor's, to possess the Sword and lead his people.
The long journey takes the three of them to an abyss, where Kor slips and loses his footing, but still holds the Sword. Worf saves Kor by grabbing the other end. Straining, he tries to convince Kor into letting go and landing on a dangerously small ledge, but Kor refuses. Dax helps pull up Kor and holds on to the sword herself as the other two are fighting over it. She holds it even as she sleeps. Dax is awakened by the sound of Worf and Kor, ready to fight to the death. Then, Worf and Kor turn on each other, and Worf is on the verge of killing Kor when Dax stuns each of them with her phaser, then transports the three of them back to the runabout. Later, on board, Worf and Kor realize that the Sword turned the two against each other, and will probably divide the Klingon people as well. They make the decision to beam the sword into space, to protect the Empire.