Dax experiences hallucinations and exhibits hostile behavior, leading to a routine life-jeopardizing medical mystery that pays off in the long run thanks to some new character development and other twists and turns.
In the most interesting Dax episode yet, the writers finally let her dark side out of the closet, something one would never know existed given the perpetually calm, cheerful demeanor Jadzia sports. Act one is entertaining and effective, proving Farrell can play Dax with an attitude. She accuses Sisko of cheating in a chess game and then dumps all the pieces to the floor. Kira tries to bring Dax to realize her recent abusive tone toward others, but Dax turns on her (hence Jadzia's once unthinkable line, "Get your hands off of me...before I do something I'll regret"). Dax finally winds up in the infirmary where Bashir uses medical technobabble to explain that her behavior is the result of an "imbalance" between host and symbiont. Further events put Jadzia's life in danger as she's rushed into emergency surgery.
Granted, the medical jeopardy plot is definitely not a new concept. It is, in fact, a Trek cliche. Through the seven years of TNG, how many times did Picard lie on the operating table with his life on the line? But "Equilibrium" is much more inquisitive than the previews make it out to be, and placing Jadzia's life in jeopardy is wisely used only as a device to launch other plot threads and explore more interesting character issues.
The mystery leads to Trek's first visit to the Trill Homeworld, where Dax is placed under special medical supervision by the symbiosis committee. One disappointing aspect here is a matte painting featuring what is supposed to be a beautiful world, but instead comes across as far too restrained by focusing mainly on a single building. Trill is also shot solely on two unremarkable sets. Is it strictly forbidden to shoot anything outdoors? Still, it's another addition to the Trek encyclopedia of worlds, and another chance to escape the station via the series' new Defiant.
The mystery grows somewhat plot- and dialogue-heavy but remains enduringly interesting in spite of some excesses, such as the slightly exorbitant notion that half the population of Trill is capable of symbiosis yet officials keep the fact under the rug to avoid anarchy over the limited number of symbionts. The conclusion reveals to Dax that one of her previous hosts—a violent-tempered musician who killed a doctor—was blocked from her memory. Jadzia allows the memories to be reintegrated into the Dax symbiont, adding to her own personality. Hopefully (but only if the writers permit it) this will profoundly change her currently underwhelming personality. Everyone needs a dark side, including Jadzia Dax.
Lastly, let's not forget the great character moments that make this one a winner. The cast works together like a well-oiled machine. The episode opens with the series' most amiable teaser yet when Sisko hosts dinner in his quarters for the senior staff. Some enjoyable tidbits include Sisko mentioning his grandfather's restaurant in New Orleans, Odo taking an interest in cooking and Kira telling the chef-apprentice shapeshifter that he looks so "cute" while mixing ingredients. Who says the DS9 crew can't be a big happy family?