Star Trek: Deep Space Nine: The Adversary

"The Adversary" is the 72nd episode of the syndicated American science fiction television series Star Trek: Deep Space Nine, the season finale of the third season. Set in the 24th century, the series follows the adventures on Deep Space Nine, a space station located near a stable wormhole between the Alpha and Gamma quadrants of the Milky Way Galaxy. In this episode, Captain Sisko (Avery Brooks) and the Defiant crew must stop a Changeling infiltrator attempting to start a war between the Federation and one of its neighbors.