Sci-fi shows that ended on a cliffhanger occupy a special place in the hearts of fans of the genre, often somewhere between obsession and heartbreak. There's nothing more frustrating than watching a series slowly unravel its complex mythology, build tension with each episode, and then drop a massive twist, only for the network to pull the plug. Whether it’s due to ratings struggles, behind-the-scenes drama, or unexpected scheduling issues, cancelation can hit hardest just as the story is hitting its stride. For sci-fi, a genre built on big ideas and long arcs, those sudden stops are particularly painful.

Over the years, several sci-fi series have left audiences stranded mid-story on frustrating cliffhangers, with timelines disrupted, alien threats unresolved, and entire universes hanging in limbo. From time-travel experiments gone wrong to post-apocalyptic power struggles and mysterious disappearances, these shows had us hooked right until the network yanked the rug out. Some were building toward answers we never got. Others dropped game-changing twists in their final moments. All of them left viewers wondering: what would have happened next? Here are the most memorable, most maddening, and most talked-about cases of sci-fi shows that ended on a cliffhanger (and left us screaming into the void).

11 Alphas (2011-2012)

Canceled After Season 2

Syfy’s Alphas centered around a group of ordinary people with extraordinary abilities (telepathy, super strength, hyper-intelligence, etc) brought together by the government to track down others like them. Think X-Men with a procedural twist. The show steadily developed its characters and expanded a morally complex world of powered individuals. After two seasons, it had laid the foundation for a full-blown civil war between Alphas and humans.

The Alphas season 2 finale delivered a killer cliffhanger: the protagonist, Dr. Rosen, broadcasts a signal to disable the powers of rogue Alphas, resulting in what looks like mass casualties. He collapses, and the episode ends with city streets filled with what appear to be bodies. Viewers were left stunned, unsure who survived or what Rosen’s fate was. Syfy canceled Alphas shortly after, leaving no resolution to the event or its fallout. The show had just crossed into a more intense, darker phase, only to be snatched away before its most important chapter.

10 FlashForward (2009-2010)

Canceled After Season 1

ABC’s FlashForward had an incredibly intriguing premise: what if the entire world blacked out for two minutes and seventeen seconds, and everyone saw glimpses of their own future six months ahead? A team of FBI agents, led by Joseph Fiennes’ Mark Benford, worked to uncover the cause of the phenomenon and prevent some of the visions from coming true. FlashForward instantly gained a fanbase for how deftly it mixed mystery, sci-fi, and character drama in a way that promised a sprawling mythology.

The FlashForward season 1 finale didn’t just drop a twist - it doubled down. Another blackout hits the world, this time with new, mysterious flashes of the future. Characters see shocking new developments: a man wakes from a coma, a little girl screams in terror, and Mark Benford is caught in a shootout at FBI headquarters. Then it cuts to black. ABC canceled the show soon after due to declining ratings, leaving fans with a world that was just beginning to unravel in exciting, unpredictable ways. The cliffhanger hinted at deeper conspiracies and expanding stakes, but FlashForward fans will sadly never know what the future held.

9 Terminator: The Sarah Connor Chronicles (2008-2009)

Canceled After Season 2

Serving as a direct sequel to Terminator 2: Judgment Day, The Sarah Connor Chronicles explored what happened when Sarah and John Connor continued their mission to prevent Skynet’s rise. With Lena Headey as Sarah and Thomas Dekker as John, the spinoff show added depth to the Terminator franchise, diving into themes of fate, artificial intelligence, and the burden of being humanity’s savior. It built a strong cult following and was lauded for its complex storytelling.

Sadly, The Sarah Connor Chronicles was cut off right as it reshaped the entire Terminator timeline. The season 2 finale sees John travel to the future, only to arrive in a timeline where no one recognizes him, because he was never there to lead the resistance. It was a brilliant twist: the war is still on, but John Connor has no legacy. With Summer Glau’s Cameron missing and characters like Derek Reese killed off, the board was reset in a daring way that promised major changes in season 3. Unfortunately, Fox canceled Terminator: TSCC due to low ratings, and the franchise never followed up on the story. It remains one of the most jarring and unresolved cliffhangers in any Terminator property.

8 Mork & Mindy (1978-1982)

Canceled After Season 4

Though best ed as a sitcom, Mork & Mindy had deep sci-fi roots. Robin Williams starred as Mork, an alien from the planet Ork who comes to Earth to study human behavior, reporting back to his superior, Orson. The show was a spin-off of Happy Days, but quickly became its own cultural phenomenon thanks to Williams’ chaotic, otherworldly energy and improvisational genius. Over four seasons, it blended heart, absurdity, and social satire.

But despite its success, ABC canceled Mork & Mindy after season 4 amid dropping ratings and creative shifts. The final episode was a total curveball: Mork and Mindy begin jumping through time to escape alien assassins. They encounter historical figures and bizarre situations before ultimately disappearing into a time vortex. That’s it - no resolution, no explanation, and no fifth season to clear things up. It was a jarring shift from the show’s usual tone and left audiences confused and disappointed. Ending a beloved comedy with a sci-fi chase through time and no closure felt like a disservice to both its characters and fans.

7 Dark Matter (2015)

Canceled After Season 3

Created by former Stargate writers Joseph Mallozzi and Paul Mullie, Dark Matter premiered on Syfy and offered a compelling mystery: six people wake up on a spaceship with no memories of who they are. As they piece together their pasts, and the fact that they’re dangerous criminals, the crew of the Raza evolves from strangers to reluctant heroes. The show grew into a smart, serialized space opera filled with betrayals, political intrigue, and AI ethics.

By the end of Dark Matter season 3, the stakes had never been higher. A new alien threat, the Black Ships, looms over the galaxy, and Earth is facing a full-scale invasion. One crew member is seemingly killed, another is taken prisoner, and the crew is scattered. Just as the pieces fall into place for an intergalactic war, the show cuts to black. Despite its growing fanbase and ambitious setup, Syfy canceled Dark Matter due to cost concerns and internal politics. Mallozzi later revealed plans for a fourth season that would’ve tackled the alien war and deeper mysteries. Sadly, fans never got to see the payoff to three seasons of carefully layered storytelling.

6 The Society (2019)

Canceled After Season 1

Netflix’s The Society dropped a group of high school students into an eerie mystery: after returning from a canceled field trip, they find their entire town devoid of adults, completely cut off from the rest of the world. Forced to fend for themselves, the teens struggle to build order while uncovering strange clues suggesting they may be in an alternate universe. The show mixed teen drama with slow-burn sci-fi, and earned praise for its character development and tension.

The Society season 1 ended with a jaw-dropping twist. Just as the teens were establishing a fragile new government, viewers are shown a glimpse of their parents alive in what seems to be the real West Ham, staring at a memorial wall listing the students as “missing.” The implication: the teens are trapped in a different reality or dimension. The Society season 2 was reportedly in pre-production, but Netflix canceled the series due to pandemic-related scheduling issues. That left the story hanging at the most crucial moment, with no answers about the town’s true nature, the mysterious dog that appeared to cross realities, or the experiment-like elements behind it all.

5 Daybreak (2019)

Canceled After Season 1

Daybreak was Netflix’s post-apocalyptic teen dramedy that combined Mad Max-level chaos with high school cliques. Set in Glendale, California, after a nuclear holocaust, the show followed Josh Wheeler as he searched for his missing girlfriend while navigating a world run by warring teen factions. Daybreak mixed a heavy dose of pop culture references with comic-book stylings, fourth-wall breaks, and zombie-like “ghoulies” to create something weirdly unique, equal parts satire and survival drama.

After one season, Daybreak delivered a major cliffhanger: Josh finally rescues Sam, only to be rejected by her. Sam declares that she doesn’t want to be saved and instead decides to seize power as the new ruler of post-apocalyptic Glendale. Just as Josh thought he’d found a happy ending, the girl he loved flips the script, setting up a fascinating second season about morality, leadership, and power struggles. Unfortunately, Netflix canceled the show just a month after it premiered, citing low viewership. The final scene redefined the entire dynamic of the show - turning the hero into the possible villain’s foil - and fans will sadly never get to see how that story would have played out.

4 The Whispers (2015)

Canceled After Season 1

ABC’s The Whispers was a high-concept alien invasion thriller with a chilling hook: an unseen entity was communicating with children and manipulating them to carry out dangerous tasks. Based on a short story by Ray Bradbury, the series starred Lily Rabe and Milo Ventimiglia and leaned into paranoia, government secrecy, and psychological horror. As the mystery deepened, the alien known as “Drill” turned out to be just one of several beings capable of influencing the youngest and most vulnerable.

The Whispers season 1 finale escalated quickly. Drill succeeds in abducting a group of children just as the government attempts to destroy his presence on Earth. The final scene shows the missing kids aboard an alien ship, lifting off into space while their families are left on the ground in anguish. It was a gut punch - a mass abduction with no immediate hope for recovery. The show was clearly gearing up for a season 2 that would shift from Earth-bound mystery to interstellar stakes. However, ABC frustratingly pulled the plug before any continuation could happen. Fans were left wondering: Where were the children taken? Could they be saved? And what was the true agenda of Drill’s species? These are all valid questions which, sadly, will never get answered.

3 Quantum Leap (1989-1993)

Canceled After Season 5

NBC’s Quantum Leap followed Dr. Sam Beckett as he leaped through time, inhabiting other people’s bodies to correct historical wrongs. With each episode, he aimed to fix someone’s past, while hoping each leap would be his last. Alongside his holographic partner Al, Sam’s journey was equal parts heartwarming and thought-provoking, blending science fiction with social commentary. It ran for five seasons and became a cult favorite. However, the final episode of Quantum Leap was anything but satisfying.

The idea that Sam was lost forever, without any real goodbye, remains one of the most bittersweet cliffhangers in sci-fi TV.

Instead of returning home, Sam leaps into a bar outside time and space, where he learns that he’s been guiding his own leaps all along. Rather than go home, he chooses to leap again - this time to right a wrong in Al’s past. Then, in a stunning blow, the episode ends with a title card revealing that Sam never returned home. No final scene, no happy reunion, no resolution. NBC had decided not to renew the show, and the producers rushed to give it some kind of closure, but fans felt robbed. The idea that Sam was lost forever, without any real goodbye, remains one of the most bittersweet cliffhangers in sci-fi TV.

2 Sunny (2024)

Canceled After Season 1

Apple TV+’s Sunny was a 2024 sci-fi mystery series that starred Rashida Jones as Suzie, a grieving woman living in a near-future Kyoto after the disappearance of her husband and son. In a twist of technological irony, she’s assigned a domestic robot companion named Sunny, which gradually becomes her only ally as she uncovers a conspiracy linked to her family's vanishing. The series blended sleek visuals, corporate intrigue, and artificial intelligence into a suspenseful slow-burn thriller.

Despite critical praise, Sunny was quietly canceled after just one season. To add insult to injury, the final episode hinted at much bigger forces at play. Suzie discovers that Sunny may have been programmed with hidden data about her family’s fate, suggesting that her husband might be alive and part of a larger plot involving rogue AI and surveillance. Just as the truth is about to be exposed, the story ends, leaving viewers hanging with more questions than answers. The show was building toward a second season full of revelations and high-tech tension, but Apple pulled the plug too soon. Fans were left with a glossy mystery and a resolution that never came.