Star Trek: Deep Space Nine season 4 was a revitalizing fresh start that saved the darkest Star Trek series and set it up for greatness. DS9 season 4 saw the addition of Worf (Michael Dorn) from Star Trek: The Next Generation, but the popular Klingon was just one of several significant changes and improvements. While not designed as such, Trekkers can look at DS9 season 4 as, essentially, a soft reboot that galvanized the series led by Avery Brooks as Captain Benjamin Sisko.
The first spinoff of Star Trek: The Next Generation, Star Trek: Deep Space Nine premiered in January 1992. Because it was set on a space station rather than a starship, DS9 was immediately controversial. Segments of Star Trek fandom rejected DS9's premise straight away and the series struggled as the "middle child" of the franchise after the launch of Star Trek: Voyager in 1995. Unlike TNG or Voyager, DS9 was a decidedly darker premise, featuring Starfleet personnel cohabitating with a motley assortment of alien characters aboard a former Cardassian space station. Unfortunately, DS9 wasn't the ratings juggernaut that The Next Generation was; by the end of season 3, ratings had fallen significantly. However, as showrunner Ira Steven Behr gained creative control over the series from DS9's creators Rick Berman and Michael Piller, he already began fixing the problems with the series: Behr got DS9 its own starship, the U.S.S. Defiant, he and his writing staff introduced the villainous Dominion, and, perhaps most importantly, Avery Brooks' Commander Sisko received his long-deserved promotion to Captain.
Captain Sisko was one of DS9 season 4's biggest changes for the better. Brooks was finally allowed to shave his head bald, which gave the Captain a fresh and commanding demeanor. Paramount decided that Sisko should have a full head of hair and be clean-shaven to avoid DS9's lead character looking like Hawk, Brooks' previous role in Spenser For Hire. (Also, Patrick Stewart's Jean-Luc Picard was Star Trek's designated "bald captain".) But Brooks was unhappy with Sisko's studio-mandated look and it was reflected in his performance. Sisko gained a goatee at the end of DS9 season 3, and by the start of season 4, Behr, Berman, and Brooks won their battle with Paramount to let Sisko be bald. The improvement in Brooks' performance was immediately noticeable; Sisko became more dynamic, powerful, and, at times, even intimidating. "I feel like a different guy," Brooks happily said about finally being able to look the way he wanted.
Star Trek: Deep Space Nine season 4 also began a run of classic episodes. Starting with the Klingons-centric two-part season premiere, "The Way of the Warrior", DS9 season 4 also delivered the touching Jake Sisko tearjerker "The Visitor", the hilarious Ferengi time-travel romp to 1940s Roswell, "Little Green Men", and the Earth-set two-parter "Homefront" and "Paradise Lost" about the Dominion infiltrating Earth and nearly instigating military takeover by Starfleet. As Star Trek chroniclers Mark A. Altman and Edward Gross praised DS9 season 4: "For the first time in the thirty-year history of [Star Trek], a season's worth of episodes was produced with a large percentage being solid storytelling. In terms of consistent quality, Deep Space Nine's fourth season is the one by which others will be measured."
Even the opening credits of DS9 season 4 were revitalized with an up-tempo remix of its majestic theme song and improved visuals so that the space station was more active, reflecting its prominence as the guardian of the wormhole and protector of Bajor. The cinematography also scaled back the gloomy shadows so that the show was brighter and more inviting, while still maintaining DS9's edginess. In addition, DS9 focused more on what would become the most diverse and fascinating cast of ancillary characters in Star Trek; everyone from Garak (Andrew J. Robinson), Nog (Aron Eisenberg), Rom (Max Grodenchik), to Gul Dukat (Marc Alaimo) received prominent storylines and began the tradition of the secondary characters anchoring their own episodes.
While Worf joining DS9 was the hook that brought new and lapsed fans, season 4 was thematically about loss. The Federation lost its alliance with the Klingons, Starfleet Lieutenant Michael Eddington (Kenneth Marshall) betrayed Sisko and joined the Maquis, Quark (Armin Shimerman) lost his standing among the Ferengi, Dukat was exiled from Cardassia, and Sisko also lost his new love, Kassidy Yates (Penny Johnson), for a time when she was convicted of helping the Maquis. But by making the vastly improved season 4 about enduring loss, Star Trek: Deep Space Nine became the series it was always meant to be and boldly took Star Trek in directions it had never gone before.