Fringe, which ran for five seasons from 2008 to 2013, is a beloved science-fiction TV series comprised of 100 episodes that contain some of the best intricate storylines and imaginative characters. The series is noted particularly for featuring sci-fi icon Leonard Nimoy as a significant recurring character on what would be the actor’s final TV series. During its original run, Fringe also spawned three comic book series, three novels, and an alternate reality game. The show often received mixed reviews from critics, and viewership dropped from 10 million to 4 million (via NY Times); however, it still developed a cult following and continues to be recognized for its ground-breaking style of storytelling.

Using a mix of procedural and serialized drama, mystery, horror and fantasy, Fringe chronicled the exploits of the FBI's Fringe Division in Boston, Massachusetts. Agent Oliva Dunham, scientist Walter Bishop and Walter's multi-talented son, Peter Bishop, used fringe science and conventional investigative methods to explore life-threatening phenomena, extraterrestrial encounters, and a parallel universe. Their cases were typically connected to the biotechnology company, Massive Dynamic, whose founder, William Bell, was Walter’s former science collaborator. Audiences cherish the series for its characters and the ways that “fringe events” impact their relationships. This aspect, along with the show’s overarching mythology, allowed Fringe to deliver several memorable episodes for the audience.

15 An Enemy Of Fate (Season 5, Episode 13)

Peter and Olivia walking down an alley in Fringe

The epic milestone 100th episode, "Enemy of Faith," brought a satisfyingly emotional ending to the series. Set in 2036, the Fringe Division faces off with the Observers for a final showdown that will determine the fate of humanity. The heroes successfully implement a plan to wipe the Observers from existence. But the victory doesn’t come without sacrifice as September is killed and Walter travels more than 100 years into the future with September’s son Michael for the plan to work. Walter mouthing, “I love you” to Peter and Peter’s receiving of the white tulip drawing are tear-jerker scenes that leave viewers with teary eyes as the screen fades to black.

14 Liberty (Season 5, Episode 12)

Fauxlivia and Lincoln talk to a woman off-screen

“Liberty” aired just before the series finale to aptly set up Fringe’s conclusion. Viewers are given the treat of seeing Olivia embark on her last trip to the parallel universe to rescue Michael from the Observers, and learning that Fauxlivia and Lincoln are happily married with a child. It’s an intense episode that exemplifies the uncanny strength and courage that Olivia has displayed throughout the previous five seasons. Plus, there are touching moments between Oliva, Peter, and Walter that reveal how much the characters have grown as individuals and as a loving and ive family. Viewers are also given a glimpse of hope as the show’s ending nears.

13 Five-Twenty-Ten (Season 5, Episode 7)

Walter, Olivia and Peter standing together in Fringe

“Five-Twenty-Ten” is noteworthy for introducing a major character twist. In an attempt to avenge his daughter’s death, Peter injects himself with a device that slowly gives him the extraordinary cognitive abilities and robotic personality of an Observer. The end of the episode is a brilliant mix of psychological thriller and horror as Olivia discovers Peter’s disturbing transformation. The story also highlights an incredible performance by John Noble’s Walter Bishop who contemplates his past mistakes while listening to David Bowie’s “The Man Who Sold The World.” The song, which is about a man who feels guilty about no longer recognizing himself, sums up the crossroads Peter and Walter find themselves experiencing.

Related: Peter Was An Observer - Fringe Theory Explained

12 The Arrival (Season 1, Episode 4)

The Observer standing on a construction site in Fringe

A central character in Fringe's mythology is introduced in the episode, “The Arrival.” It’s an intriguing look at September, the mysterious eye-browless Observer, who quickly devours a raw roast beef sandwich with Tabasco sauce, jalapeños, and an entire container of black pepper. An Observer’s ability to predict future events establishes the show’s main plot thread and fosters a compelling conversation about predestined events and free will as the characters make choices throughout the series to alter disastrous outcomes. Audiences also catch a glimpse of how September is different from the other Observers, a foreshadowing of how his actions will impact the lives of Oliva, Walter and Peter.

11 Subject 9 (Season 4, Episode 4)

Fringe Subject 9

In retrospect, Fringe's “Subject 9” stands out for featuring iconic blockbuster and TV star Chadwick Boseman, who was relatively unknown at the time the episode aired. Boseman plays Cameron James who, as a child, was a subject of Walter Bishop's Cortexiphan drug trials, designed to draw out a person's latent powers. Imbued with the capability of affecting the electromagnetic field whenever he becomes upset, Cameron unknowingly brings back Peter Bishop who was previously erased from existence in the Season 3 finale. Audiences anxiously awaiting Peter’s return are rewarded at the episode’s end when the beloved hero suddenly emerges from the waters of Reiden Lake.

10 The Abducted (Season 3, Episode 7)

Phillip Broyles looking serious in Fringe

Fringe incorporates various genres in its stories and “The Abducted” is a solidly entertaining psychological thriller. The episode also shows audiences the more human side of Broyles and deepens the relationship between him and Olivia (even though she is interacting with the parallel universe version of her boss). The story takes audiences on an edge-of-your-seat ride of twists and turns that ultimately reveals that the serial killer Oliva and Broyles are hunting is a minister. “The Abducted,” is also a turning point for Peter who finally realizes that the woman he’s been dating is not Olivia, but Fauxlivia from the alternate world.

9 Welcome To Westfield (Season 4, Episode 12)

The group standing in an alley in Fringe

“Welcome to Westfield” is a classic Twilight Zone type of episode that finds Oliva, Walter and Peter trapped in a small town that is being affected by the colliding of the prime and parallel universes. It’s a chilling tale that tests all three characters' resolves and is a turning point in the series following Peter’s return to his original timeline. Audiences are delighted to see Olivia and Walter’s slowly regain their memories of Peter and their past cases together. The episode also provides a hint that what Peter thinks is an alternate timeline is actually his own, and that this Olivia and Walter are the same people he’s always known.

8 Jacksonville (Season 2, Episode 15)

An image of Olivia standing in a classroom in Fringe

“Jacksonville” is a nail-biting story that shows one of Anna Torv’s strongest performances as Oliva. The episode is a traditional superhero story in which Olivia returns to the clinic, where drug trials are conducted on her and other children. Angry with Walter over the experiments, Olivia is doubtful she’ll be able to channel her powers to prevent a universe-colliding event. “Jacksonville” skillfully delves into Olivia’s childhood self, which proves to be the key to unlocking her abilities in time to save the occupants of a soon-to-be-disappearing apartment building. The episode also marks a key turning point in the series as she realizes that Peter is actually from the parallel universe.

7 Over There: Part 2 (Season 2, Episode 23)

William Bell using his powers in Fringe

The second part of the Fringe team’s journey in the parallel universe reminded audiences of how Leonard Nimoy is a sci-fi legend. While Nimoy’s William Bell shares the same intelligence as Star Trek’s Spock, the founder of Massive Dynamic also possesses characteristics that the famous Vulcan doesn’t, like charm, wit and empathy. Audiences are able to see Bell’s full personality on display as he spars with Walter who is sometimes too rigid and over-analytical like Spock. The episode ends with the revealing twist that Fauxlivia has infiltrated the prime universe and Olivia is being held captive in the parallel one.

6 Over There: Part 1 (Season 1, Episode 22)

Olivia, Charles, and Boyle standing together in Fringe

“Over There, Part 1” finds the Fringe team traveling to a parallel universe for the first time in an effort to find Peter, who has crossed over upon learning the truth of his origins. Audiences are also introduced to Olivia, Charlie, and Boyle’s doppelgängers and a new character, Agent Lincoln Lee. The Fringe cast, particularly Torv gives another robust performance as both Olivia and Fauxlivia throughout the episode. Seeing both characters on screen emphasizes how different Olivia is from her counterpart. Whereas Olivia is cautious and reserved, Fauxlivia is free of inhibition and blunt with her opinions; these major differences signal to viewers that a game of deception is about to begin.