Spinning out of "Star Trek: The Next Generation," "Star Trek: Deep Space Nine" expanded the iconic science fiction franchise into considerably darker and more morally ambiguous territory than its predecessors. Starring Avery Brooks as Captain Benjamin Sisko, the show took place on its eponymous Starfleet space station positioned by the planet Bajor and a wormhole leading to the Gamma Quadrant. As the series progressed, "DS9" would shift to longer-form storytelling as the installation became a focal point amidst the Starfleet and the Dominion's warfare.

With over 170 episodes across seven seasons, "DS9" had a memorable ensemble cast that pushed the final frontier into new directions that its successors thematically furthered, including "Star Trek: Voyager." From standalone character studies to emotionally searing tales of battle and sacrifice, "DS9" ran a wide gamut of themes and tones that redefined what "Star Trek" could and can be while earning a considerable amount of widespread acclaim. Here are the 15 best episodes of "DS9" that I consider the best showcase of the series' ambitious story.

In Purgatory's Shadow (Season 5, Episode 14)

A war between Starfleet and the Dominion and an alliance between the Cardassian Union and the Changelings — the same shape-shifting race as Odo (René Auberjonois), based in the Gamma Quadrant — had been brewing since season 3. By season 5, the conflict between the two factions became inevitable, with hostilities escalating dramatically in the "In Purgatory's Shadow" episode. Packed with twists and deception, "In Purgatory's Shadow" is one of the most shocking episodes of "DS9." The episode showcases Starfleet's peaceful ideals violently tested.

While investigating a distress signal from the Gamma Quadrant, Worf (Michael Dorn) and Garak (Andrew Jordt Robinson) stumble across a Dominion invasion fleet poised to enter the Alpha Quadrant — leading to their imprisonment. Worse, Doctor Bashir (Alexander Siddig) and Klingon General Martok (John Garman Hertzler Jr.) are imprisoned, revealing Changeling imposters have secretly taken their place in the Alpha Quadrant. A lot is going on in "In Purgatory's Shadow," but the episode is a masterclass in juggling multiple payoffs and reveals without them overshadowing each other. This episode sets the stage for something great to follow.

Improbable Cause (Season 3, Episode 20)

Odo's responsibilities as DS9's constable usually lead him to match wits with whichever illicit get-rich scheme Quark (Armin Shimerman) has cooked up next. But Odo finally gets a chance to showcase how keen a crime-solver he is in "Improbable Cause." After someone attacks Garak's tailor shop, Odo investigates who is behind the explosive assassination attempt. As Odo gets closer to the heart of the mystery, he stumbles across a wider conspiracy that leaves him unsure of who to trust, including Garak.

More than just an excellent showcase for René Auberjonois' Odo, "Improbable Cause" is instrumental in establishing Andrew J. Robinson's Garak as a vital addition to the "DS9" cast. Garak had been a recurring presence on the series since episode 3: He hints at having a dark past, but this is unmistakably brought to the forefront here. Odo and Garak didn't get to share scenes often, and their pairing in a whodunnit makes for an entertaining team-up of a detective hunting the truth with a spy unable to tell it.

The Siege Of AR-558 (Season 7, Episode 8)

Often, "DS9" cited the mounting cost of the Dominion War as the conflict progressed across the show's latter seasons. But the horrors arrive front and center in season 7's "The Siege of AR-558." On a routine mission to provide supplies to a planetary communications installation, the crew becomes embroiled in a brutal ground battle against the attacking Jem'Hadar. Impressionable Ferengi Starfleet recruit Nog (Aron Eisenberg) plays a vital role in the bloody fight, losing a leg throughout the fiery skirmish and witnessing other wartime nightmares firsthand.

"The Siege of AR-558" is a meditation on the end of innocence and war's hollow gallantry — a sort of "All Quiet on the Western Front" by way of "Star Trek." Sisko and other main characters often lament casualty reports and other news of the war. But in this episode, they encounter their most harrowing battle ever — even Quark becomes involved. "The Siege of AR-558" blends rousing set pieces with reflections on trauma, illustrating the ramifications of the Dominion War storyline.

Take Me Out To The Holosuite (Season 7, Episode 4)

If "The Siege of AR-558" stands among "Deep Space Nine's" darkest episodes, "Take Me Out to the Holosuite" is a reminder of how much escapist fun the show provides. In a rare respite from the Dominion War, Sisko reunites with Solok (Gregory Wagrowski), an old rival who believes he (and his Vulcan crew) are empirically superior to their counterparts. Determined to beat the elitist Starfleet captain, Sisko takes on Solok's crew in a pickup game of baseball with the DS9 team in the Holosuite.

"Take Me Out to the Holosuite" works most effectively when taken into the context of the series. By its seventh season, "DS9" had become a bonafide war show. Sisko and his allies constantly make compromising and costly decisions against the Dominion, changing galactic stakes. This baseball diversion offered a refreshing detour from the show's bleak tone and let characters explore their fun side again in a low-stakes side story.

By Inferno's Light (Season 5, Episode 15)

If "In Purgatory's Shadow" shocked audiences with multiple twists about the Dominion's clandestine tactics to destabilize Starfleet, its immediate follow-up, "By Inferno's Light," solidly resolves loose ends while upping the ante. After learning Bashir and Martok have been replaced by Dominion imposters, there is a heightened sense of intrigue — as most characters don't know this truth. This episode finds its balance with a more grueling story: Worf and Garak endure the horrors of imprisonment.

As the disguised Changeling, Alexander Siddig shines in a darker performance as a disguised villain — secretly charged with carrying out one of the series' most dastardly schemes. Dorn similarly delivers one of his best performances as Worf. He's defiantly unwavering, no matter how much punishment the character suffers in captivity. A massively important chapter in progressing the overarching Dominion War narrative and filled with great character moments, "By Inferno's Light" signals how dark and intense "DS9" later becomes.

The Die Is Cast (Season 3, Episode 21)

Continuing the story from "Improbable Cause," Odo and Garak discover a Cardassian-Romulan armada attacking the Dominion. As the two men's absence becomes acutely apparent for the DS9 crew, Sisko defies Starfleet Command to bring Odo safely home from the Gamma Quadrant. If "Improbable Cause" is a glorified whodunnit, "The Die Is Cast" is a full-on war story and one of the best in a series that would eventually become defined by them in its latter half.

More than just continuing to capitalize on the onscreen pairing of Odo and Garak, "The Die Is Cast" solidifies that multi-part storytelling has a place in "Star Trek." Apart from the occasional two-parter, "Star Trek" focused on episodic storytelling. "DS9" trailblazed longer-form storytelling that the current "Star Trek" on Paramount+ utilizes. Beyond its franchise implications, the episode is a rousing tale that offers compelling character moments for Odo, Garak, and Sisko as the Dominion War's foundations take shape.

The Way Of The Warrior (Season 4, Episode 1)

Although the main "DS9" cast is memorable and effectively tight-knit, the entire show received a significant boost with the addition of Michael Dorn reprising his "TNG" role as Worf. This fresh arrival came in the season 4 premiere, opening with the Klingon Empire going to war with the Cardassian Union. Looking for additional insight into Klingon policy and culture, Sisko has Worf transferred to DS9 to learn what the Klingons have planned for the escalating conflict.

"The Way of the Warrior" features a role-defining performance from Dorn: He takes full advantage of his character's torn loyalties between Starfleet and the Klingon Empire. Worf has always been a figure caught between cultures, but by the episode's end, Worf has committed to a side. Dorn brings moral complexity to Worf reaching that decision. Dorn fit seamlessly into the "DS9" cast and story from the jump, and "The Way of the Warrior" provides him the perfect showcase to cement why he belonged off the Enterprise.

Far Beyond The Stars (Season 6, Episode 13)

"Star Trek" has never been a franchise shy of providing social commentary. However, it almost always does this through the veneer of science fiction, using cosmic metaphors to make its messages less overt. But season 6's "Far Beyond the Stars" discarded all sense of allegorical subtext to present a pointed rebuke of racism and bigotry in a standalone episode directed by Avery Brooks. As the pressures of the Dominion War take their toll on Sisko's psyche, he fantasizes about being science fiction writer Benny Russell in 1953's New York City.

From Patrick Stewart to Kate Mulgrew, "Star Trek" has boasted several classically trained stage actors in their principal roles, and in that regard, "DS9" is no different. The cast takes advantage of playing new characters in a standalone period-piece story largely separate from the main narrative. Brooks gives the most powerful performance of his time on the show. A bold portrait of what "Star Trek" can be and has always stood for, "Far Beyond the Stars" is an emotional powerhouse that lets its cast showcase their fine acting chops.

What You Leave Behind (Season 7, Episodes 25/26)

"Star Trek" often pulls out all the stops for its series finales, and "DS9" is no different. However, it ends on a more fittingly bittersweet note than "TNG" and "Voyager." In the "DS9" series finale, Starfleet launches its final offensive in the Dominion War. Kira (Nana Visitor) embarks on a daring mission on Cardassia Prime to turn the Cardassian Union against their Dominion allies. As the devastating war reaches its fiery climax, Sisko has one final confrontation with Dukat (Marc Alaimo), embracing his destiny as foretold by the Bajoran prophets.

A good series finale not only resolves its major plot threads but gives each of its leads one last character moment before the end credits roll: "DS9" deftly succeeds with this. Each character gets a moment to shine in the closing moments of the Dominion War while Sisko fulfills the spiritual role teased since the series premiere. Though its somewhat obligatory deaths may seem like a cheap way to raise the stakes, "DS9" ends on a high note that lives up to the melancholia that defined "DS9."

Sacrifice Of Angels (Season 6, Episode 6)

The fifth season of "DS9" ended with a shocking cliffhanger: The Cardassians led the Dominion to seize control of DS9. Starfleet personnel retreated as the Dominion War swept across the Alpha Quadrant. Season 6 kicked off with a six-episode storyline following DS9 under Cardassian occupation, culminating with Starfleet retaking the space station in "Sacrifice of Angels." With Sisko at the helm of a Starfleet armada pitted against Dukat's opposing Cardassian fleet, the episode is as thrilling as "DS9" gets while keeping an eye on personal stakes.

Brooks stands front and center as Sisko shifts into a hardened wartime leader. Sisko finally squares off against Dukat on the battlefield, gambling with the lives under their respective command. Marc Alaimo plays Dukat to the hilt, bringing the character to his most emotionally vulnerable as he loses his daughter amidst the horrors of war. By the end of "Sacrifice of Angels," Sisko and Dukat emerged as changed men: Their longstanding feud more bitterly personal than ever — giving the interstellar conflict its raw heart.

Duet (Season 1, Episode 19)

"DS9" is a show borne in fire and blood — not just for the Sisko family but for the Bajorans liberated from the Cardassians' lengthy and brutal occupation. Bajoran security officer Kira Nerys' painful history with the Cardassians is explored in season 1's "Duet," serving as a transformative moment for the character. Confronted with an alleged Cardassian war criminal, Kira becomes determined to bring the notorious figure to justice at any cost, even as doubts over his identity surface.

"Duet" operates as an inversion of the "TOS" episode "Conscience of the King," which similarly saw Captain Kirk investigate a man he suspected of being a fugitive war criminal. However, "DS9" keeps its audience guessing over the validity of these suspicions by highlighting that war leaves victims on both sides. These themes help add further human dimensions to Kira and hint at the darker direction "DS9" would eventually assume when the Dominion War takes center stage in the series.

The Visitor (Season 4, Episode 2)

"DS9" begins with Sisko losing his wife to the Borg, leaving him with their young son, Jake (Cirroc Lofton), as the two face their shared grief. We see the depth of Jake's love for his father in the season 4 episode "The Visitor," with the elder Sisko lost to a temporal anomaly while on a routine mission observing a wormhole. As his father periodically appears to him briefly throughout his life, Jake becomes obsessed with finding a way to rescue Benjamin at any cost.

A reflection on the bond between fathers and sons, "The Visitor" is "DS9" at its most emotionally resonant. Cirroc Lofton and guest star Tony Todd excel in their performances as Jake as he grows up. More than just a fantastic standalone episode of the series, "The Visitor" is a remarkably well-written sci-fi story in the "Twilight Zone" or "Time Traveller's Wife" mold. "DS9" was always "Star Trek" at its darkest and most tragic, and "The Visitor" paints a story with those painful colors beautifully.

Call To Arms (Season 5, Episode 26)

Although there have been hostilities between Starfleet and the Dominion before, the Dominion War officially commences in the season 5 finale, "Call to Arms." The episode puts the Federation immediately on the defensive. After drawing the battle lines, Sisko becomes tasked with mining the nearby wormhole to the Gamma Quadrant to prevent the Dominion from linking the bulk of their forces with Cardassia. With Starfleet and the Klingon Empire occupied, Sisko must hold out as long as possible to ensure his mission is successful.

Ever since "The Wrath of Khan," "Star Trek" has become fascinated with the idea of a no-win scenario to see how its main characters react to impending defeat. Hopelessly outnumbered and with no expectation of reinforcements, Sisko and his allies know they're going to lose DS9 to the Dominion. It's only a matter of when. "DS9" is widely remembered for becoming a war show, and "Call to Arms" masterfully handles that transformation as its characters admirably engage in a holding action they know will end in defeat.

Trials And Tribble-Ations (Season 5, Episode 5)

One of the best episodes in all of "Star Trek," not just "DS9," is season 5's "Trials and Tribble-ations," commemorating the 30th anniversary of the franchise memorably. The DS9 team travels back to the events of the "Star Trek: The Original Series" episode "The Trouble with Tribbles" and interacts with the classic crew to prevent the timeline from being disrupted and altering history. An impressive feat in technical production and storytelling, "DS9" crafted a franchise tribute that has yet to be topped.

Using the same digital insertion technology as "Forrest Gump," "Trials and Tribble-ations" takes up the same sense of humor as the "TOS" episode with self-aware flair. Commentary about the physical changes of Klingons and the admittedly dated "TOS" era Starfleet uniforms surface. "DS9" handles the shift to sci-fi comedy wonderfully. More than offering a timely celebration of all things "Star Trek," the episode has a rare moment of levity before "DS9" moves into considerably darker tones for the remainder of the series.

In The Pale Moonlight (Season 6, Episode 19)

From black ops divisions to engaging in biological warfare, "DS9" pushed the boundaries for how dark "Star Trek" could go, clashing with the utopian ideals of the Federation. At the center of this narrative evolution is Sisko, a traumatized veteran who lost everything to wartime tragedy only to become a leader performing increasingly morally dubious acts to ensure victory. Season 6's "In the Pale Moonlight" perfectly showcases this transformation and the show's overarching darkness. This episode reveals how ruthless Sisko has become to serve the greater good.

With Starfleet steadily losing ground to the Dominion, Sisko and Garak devise a plot to trick the Romulan Empire into entering the Dominion War allied with the Federation. Framed as the recording in Sisko's personal log after the fact, "In the Pale Moonlight" plays out like a confession by the character. Pushing the moral boundaries of "Star Trek," the episode is a masterclass in how it directly challenges its characters' souls while asking what happens when good people go to war.

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