10 Greatest Star Trek Bottle Episodes
4. The Adversary
Closing out Deep Space Nine's third season is the paranoid thriller The Adversary. While there had been other plans for the season's end that were put on hold, though would eventually surface as Homefront and Paradise Lost, this show - set almost exclusively aboard the Defiant - truly ratches up the threat of the Changelings.
Lawrence Pressman returned to Deep Space Nine, having previously appeared as Tekheny Ghemor, as Ambassador Krajenski, at least to start with. The episode borrows from The Thing From Another World, the 1951 adaptation of John W. Cambell Jnr.'s Who Goes There? The isolation, along with the very real threat that the coopted Defiant poses, helps to build the tension throughout.
The episode also builds on the premise that 'no Changeling has ever harmed another' - a phrase that had been repeated several times through the series' third season. Odo and 'Krajenski's' final fight in engineering sets one of the largest plot threads in Star Trek history into motion, not least with the final warning - you are too late. We are everywhere.
That the episode achieves its aims while barely leaving the Defiant's confines is a triumph.