Star Trek: Deep Space Nine: "The Adversary"

It's 19 June 1995, and time for the season finale of Star Trek: Deep Space Nine.

A newly promoted Captain Sisko (Avery Brooks) is ordered to take the Defiant to the Federation's border with the Tzenkethi, an alien civilization that has fought a war with the Federation before. En route it becomes clear that someone has sabotaged the ship. Now Sisko commands a race against time to track down the shapeshifting saboteur before the Defiant is used to spark an all-new war.

Season 3 comes to a close with a tense, action-packed homage to John Carpenter's The Thing. The crew of the Defiant are trapped in a similarly closed-off, isolated environment with no escape, and any one of them could be a changeling. It apes the film's claustrophobic hunts for the hidden monster, and blatantly copies its blood test sequence. How much you enjoy this episode will likely depend on where you think homage ends and plagiarism begins.

The episode begins with Sisko's promotion, which does feel somewhat overdue. It always seemed odd that Starfleet would entrust a commander with the security of a strategically significant wormhole on the border of a civilization that was only fighting a war with the Federation just over a decade ago. To be honest I think it was only ever planned as a point of difference between Deep Space Nine and its predecessors: Star Trek and The Next Generation had captains, so DS9 got a commander. With The Next Generation off the air and Voyager featuring the franchise's third captain, I suppose they finally felt the point of difference wasn't worth it.

The episode gets off to a slightly weird start from there, since a Federation ambassador (Lawrence Pressman) informs Sisko that the Tzenkethi homeworld has undergone a violent coup d'etat, and the Defiant needs to shore up the Federation's border with the Tzenkethi in case this latest development kicks off another full-blown war. It's odd, because the episode seems to expect us to know who the ambassador is (we don't), and acts as if the unrest among the Tzenkethi is a worrying development. We've never heard of the Tzenkethi. We don't actually get to see them in this episode. To the best of my knowledge they're never mentioned again. It all seems to be a haphazard excuse to get everybody onto the Defiant so that the real episode can begin.

Once the ship has been sabotaged and the paranoia is ratcheted up, "The Adversary" rattles along in a pretty entertaining fashion - certainly entertaining enough to paper over any of its faults. It arguably does copy too much of The Thing to really get away with being an homage, but it's repurposed well and fits with the overall narrative. The identity of the secret changeling is never really in doubt, unless you're a particularly credulous viewer.

It's at the episode's climax that things really pick up. Throughout the whole season we've been repeatedly told 'no changeling has ever harmed another'. It's referenced again halfway through this episode. On top of that, Odo explains to Lt Commander Eddington in this episode that he's never felt the need to use a gun, and in his entire career as a security specialist he's never once had to kill somebody. It's laid on remarkably thick, yet even when the inevitable moment comes it's an immensely powerful moment. Rene Auberjonois sells it brilliantly to the camera: Odo is shocked, heartbroken but also resolute. His is one of Deep Space Nine's finest ongoing performances.

And shortly after that, Season 3 ends. The dying changeling has left Odo with a worrying warning: 'you're too late, we're everywhere'. And there the break before Season 4 begins, with enormous uncertainty and rising dread. There were 26 episodes in Season 3, and by my reckoning 18 of them - including this one - were good. That gives the season a final quality ratio of 69 per cent: somewhere behind Season 3 (77%) but ahead of Season 1 (63%).