Apocalypse Rising

Believing that Klingon chancellor Gowron has been replaced by a changeling, Sisko leads a covert mission to expose him. Disguised as Klingons, Sisko, Odo, O'Brien and Worf infiltrate Ty'Gokor, the Klingon military headquarters, during a ceremony of the Order of the Bat'leth. They carry radiation emitters which will force any changeling nearby to reveal itself. When the devices are destroyed, the mission looks doomed, but General Martok confides that he too suspects Gowron. Worf challenges Gowron to combat, hoping to expose him, but at the last moment Odo realises they have the wrong target: a changeling would not behave with Gowron's sense of honour. The impostor is Martok, and once exposed it is killed. Gowron accepts that the Federation was fed false intelligence about him, a deception that would have helped the Dominion gain control of the Klingon Empire, and a ceasefire between the Klingons and the Federation is agreed.