Season synopsis
Contains spoilers for this season and earlier seasons.
General Martok brings a Klingon fleet to Deep Space Nine, prompting Sisko to call in Worf to discover its purpose. Cardassia’s civilian Detapa Council has overthrown its military rulers, but the Klingons claim the new government is controlled by Changelings and invade. Federation condemnation leads Gowron to abandon the alliance. Sisko rescues the council and defends the station when Gowron attacks despite evidence that its guests are not Changelings. Worf refuses to join the invasion and stays with Starfleet as the station’s strategic operations officer.
A Changeling bombing on Earth brings Sisko and Odo into an emergency that Admiral Leyton exploits to seize power. With help from Nog’s cadet connections, they uncover Starfleet officers manufacturing evidence of an invasion. Leyton has Sisko imprisoned as a supposed Changeling, but Odo frees him. The Defiant brings a witness toward Earth, and the captain of the pursuing Lakota refuses orders to destroy it. Leyton resigns and the emergency measures are lifted, exposing how the fear of infiltration nearly handed him the government.
In “Broken Link,” Odo’s body begins failing, and he travels with Bashir and Sisko to the Founders’ homeworld for judgment after killing one of his own kind. The Founders made him ill to force his return; after the Great Link judges him, they cure the illness by making him a solid, taking away his ability to change shape. Back at DS9, Odo interprets what the Founders hid from him as evidence that Gowron is a Changeling. The season closes on that unconfirmed suspicion and a new Klingon threat, leaving the station on combat alert.