J.J. Abrams’ Fringe was an extraordinarily innovative sci-fi series, filled with mind-blowing pseudo-science, heart, and slick action. However, its first season was a procedural, in order to feel more accessible. And yet, even after breaking that conventional formula in season two, some incredible investigations still emerged. It is surprisingly easy to invest in the ensemble of fantastical characters, for their comedy, determination, and flaws. This keeps everything grounded, no matter how bizarre the cases get.

It’s quite the magic trick, how this show consistently translated the impossible with fun, convincing theories. Here’s the ten wildest cases that ever boggled our minds—something this show achieved with unique dexterity. Spoilers!

Bound

The first season bears many “traditional” cases which established the tone of this show, if not its truest identity. But this episode has a simple, creative, and certainly repulsive concept. In this episode, Olivia gets some great action as she escapes capture. While investigating her abduction, the team runs into a related murder. Someone has used a supersized cold virus to kill someone.

The lecture sequence is especially memorable, as the CGI and sound effects are gleefully disgusting. The slimy virus pushes its way out of the victim’s mouth and slithers away. It’s so effective, the concept was totally replicated with a giant roundworm in the second-season episode “Snakehead”. Unfortunately, there’s certainly no cure for the common cold.

Jacksonville

The parallel universe was a crucial, innovative addition to the series’ mythology, frequently inspiring the best the show could offer. Alternate timelines are innately intriguing already, but the deliberate line between just two similar universes created superb drama. In this stunning premise, the connective tissue between the two universes has merged building and people together.

It’s visually arresting, and a conceptually thrilling issue. The ticking clock of an impending follow-up disaster also drives some great backstory for Olivia’s childhood. This adds context to Walter’s ethical mishaps in the past. Also, Olivia finally learned the truth about Peter, which gradually fueled great character development.

The Ghost Network

The main premise of this case isn’t quite as groundbreaking as later investigations. At some point, Walter helped to create a secret frequency range for covert messages. One unlucky man has happened to tap into it, and he’s suffering.

However, the disasters he envisions are truly startling. This was the first appearance of “amber”, wherein a gas erupts and solidifies everything within its grasp. It’s a very creative crime scene, and ultimately, this becomes absolutely central to the show’s mythology. It was vital to the alternate universe, and even in season five’s plans. Amber was a frightening, inventive, and iconic addition to the show.

Through the Looking Glass and What Walter Found There

The fifth season’s taut storytelling provided some of the show’s brightest moments. The pacing was improved, the family dynamic was stressed, and the Observer plot was terrific. In this episode, Walter removes a tape from amber that sends him on a wild journey into a pocket universe. This pocket universe is a disorienting, surreal place, and Walter runs into the strange Observer-like boy from season one. The fifth season was heavy on well-executed fan service.

The brisk pace of this episode is incredible, as our team races the Observers to find Walter. Natural laws of reality are totally distorted. We also get Observer-vision for a minute, and Peter’s foray into Observer abilities is definitely striking.

The Day We Died

Brad Dourif, known as Chucky from the Child’s Play franchise, superbly plays the leader of a cult. Rather than a Cult of Chucky, his followers bear the lame moniker “End of Dayers”. However, their intent and methods are interesting nonetheless. At the behest of “Walternate”, they are intentionally destabilizing the universe’s soft spots. This season three finale was a complete flashforward, but it isn’t just a vision.

Peter actually lives through the horrendous events that will occur, and a temporal paradox is the only way to prevent them. The Doomsday Machine turned out to provide some inventive storytelling. We also learn the truth of the First People legend, and Peter’s abrupt disappearance was a very creative cliffhanger.

White Tulip

Peter Weller is a fantastic character actor, known best for Robocop. But he’s shown up in Star Trek Into Darkness as well, establishing the J.J. Abrams connection. In this episode, the series flaunts how well it can handle time travel. Weller’s character is attempting to rescue his wife using the technology, which has grotesquely mutilated his body. But it also accidentally kills an entire train of people, while draining the power from everything on board.

It’s a great setup, and although the situation seems rote, it’s handled very well. It also serves as a great parallel to Walter’s ethical issues about Peter. The result is one of the most meaningful episodes of the entire show.

The Road Not Taken

In this memorable episode, the case itself is once again more of an aside to the craziest ingredients. Although, the show did find a pseudo-scientific theory for spontaneous combustion, which is undeniably impressive. It’s ultimately a result of experimental attempts to generate pyrokinesis.

However, the most mind-blowing thing about this episode is undoubtedly Olivia’s strange visions throughout. It was in this episode that all the clues come together, and establish the possibility of the parallel universe for the first time. At first, fans wouldn’t realize just how significant this turn of events truly was. But it was certainly the most appealing way to introduce such a fantastic theory.

Letters of Transit

Without warning, an abrupt glimpse of the future is thrust upon the audience. The entire concept of season five was established in a single, compelling story with a great protagonist. Etta isn’t just a great actress, but very well casted for her likeness to Peter and Olivia. This episode promised the network and fans what was in store, sans cancellation. It’s a bold move, and the Observer plot is an ingenious use of time travel.

As dark as this show could be, this dystopian future is easily the darkest chapter for our heroes. The episode was totally unexpected, creative, and action-packed. It would have been an absolute shame if we didn’t have the opportunity to explore this terrifying vision.

The Arrival

There’s no question that the Observers were the greatest mystery of the show. This is because they were generally an aside, rather than directly incorporated into the plot. Their behavior and appearance is strange, to be sure. But the Observers’ actual purpose and origin remain concealed for quite a while.

In this early episode, a strange “Beacon” device is the driving plot. Its design is unsettling, and its intent is certainly confusing. Further, Walter eventually reveals that these strange people have ties to his past, regarding Peter. This episode establishes the course for a very convoluted history of Peter’s origin and future Observer mythology.

Lysergic Acid Diethylamide

Ah, yes, the continued tradition of the nineteenth episode being utterly bonkers. This is the episode with all of the animation. Olivia has been possessed, and in order to rescue her mind, Walter and Peter have to literally enter it. And in order to do that, they take LSD. This is easily the most bizarre case of all, and it involves Olivia herself. The mind is always a unique, unnatural, haphazard place to visit.

Few things feel assembled and cohesive there, so much of this story is consequently abstract. Besides the concept of possession itself, the journey through Olivia’s mind was a brave risk and resulted in absolute craziness.