The Klingons have been allowed to send a diplomatic team to System 7348 to make contact with the native, Klingon-descended, population. The Enterprise is sent to keep an eye on proceedings but gets diverted to rescue a group from the Anti-Federation League who had entered Klingon space to negotiate with them, but had ended up as captives facing torture. The rescue is successful, but it means that the Klingon ship, the D'k Tahg, arrives at System 7348 ahead of them. The Klingon ‘diplomatic team’ is led by Councilor Duras, who also has a large number of his own troops on the ship, and Captain Koloth and his second-in-command, Karel, are strongly suspicious of his motives. Before the Klingons arrive, the leader of the largest tribe, Gorath, is killed by Gurn who had been in contact with Duras, but Gorath's son, Adon, reluctantly becomes leader of Gorath's clan and leads the fight against Gurn, who has convinced the majority of the population to follow him. Adon realizes that the Klingons are planning on taking the dilithium they have mined, so he absconds with it and ends up giving it to Kirk. While Duras is annoyed at this, his main plan was to destroy the planet and its inhabitants and pass the blame on to the Federation, giving good pretext for starting a war against the Federation. As part of that plan, his men take over the D'k Tahg and strand Koloth, Karel, and the loyal crew on the planet. After the Enterprise emerges victorious from a battle against the D'k Tahg, the Enterprise is able to rescue the stranded Klingons, who then join the Federation away-team in fighting Duras's men. Fuller, who is now acting-head of security, leads the team to stop the kinetic explosive device that Duras has set to destroy the planet. Fuller had been more set on revenge than rescuing the planet and sees this as a suicide mission, but he has second thoughts and does destroy the kinetic explosive device. His team disobey his orders and rescues him, and he becomes the hero of the day. Adon end up as leader of the indigenous Klingons, and Bethe, who had fought by his side, looks like becoming his bride, and the Federation has Klingon-descended allies. Meanwhile, Ambassador Fox and his team had been rescued from the space station where they had futilely been trying to negotiate with the Klingons. [Timeline: Stardate 3197.2]