It's hard to believe it's been more than 30 years since The X-Files first aired, introducing us to a pair of young F.B.I. agents investigating the unknown — plucky Fox Mulder (David Duchovny), a conspiracy-prone believer whose sister was abducted by aliens; and skeptical Dana Scully (Gillian Anderson), whose religious faith never got in the way of her steely demeanor.
The show initially ran for nearly a decade, eventually shedding both leads. It would return (with Anderson and Duchovny) for a pair of seasons beginning in 2016. That's a lot of mysteries! Even harder than untangling the vast government cover-up is choosing 11 essential episodes from this classic show.
Over the years, The X-Files braided many tones and genres into weekly cases; one week could be uproariously funny, the next so scary that you'd have to watch between your fingers. (We will largely be sidestepping the episodes that advanced the series' internal, ongoing mythology in favor of more standalone, "Monster of the Week" episodes.)
This list (ordered by airdate) attempts to file all that The X-Files was and, should it be revived again, all that it could be. With Halloween creeping around the corner, here are some of Mulder and Scully's scariest and most essential cases you should watch before October 31.
"Squeeze"/"Tooms"
Original air dates: September 24, 1993 ("Squeeze"), April 22, 1994 ("Tooms")
Tooms (above) was the first X-Files villain to get a sequel episode
"Squeeze" was only the third episode of the series — ever! — and many believe it to be among the greatest "Monster of the Week" installments.
What's incredible is that the creatives brought back the creepy character later that same season, in a very rare move. (There were some two-part X-Files episodes, and this is probably the only one that followed half a season after the first.) But the character of Eugene Tooms — who, when he's not hibernating, can stretch and squeeze his body through very tight spaces (like an air vent or doggy door) in his pursuit of human livers — was just too fascinating to discard after a single episode. "Tooms" is an inventive (and shocking) sequel to "Squeeze," as the baddie and Mulder have one final, gory showdown involving an escalator. Both installments are load-bearing columns of the series and worth watching together.
"Ice"
Original air date: November 5, 1993
Mulder and Scully take on parasitic worms in "Ice."
This chilling, claustrophobic tale offers The X-Files' take on John Carpenter's The Thing, as the agents struggle through mounting paranoia to contain a parasitic ice worm unearthed my a team of Arctic researchers. Directed by David Nutter, who also helmed the series pilot, "Ice" is a standout "Monster of the Week" entry with incredibly effective set pieces and performances, especially from future 24 actor Xander Berkeley and future Desperate Housewives star Felicity Huffman.
"E.B.E."
Original air date: February 18, 1994
A scene from "E.B.E.," an early alien mythology episode. 
It's hard to believe, but when The X-Files started, there were standalone UFO stories untethered from the overarching mythology of the series. "E.B.E.," while featuring an appearance from Deep Throat (the late Jerry Hardin, both cuddly and sinister) and a gesture toward the larger conspiracy, is a standalone alien episode. It features a scary, mostly invisible alien let loose after a UFO crash. (One of the cooler, creepier aspects of "E.B.E." is Deep Throat acknowledging that, since Roswell, the government has ordered the extermination of every alien that lands on earth.)
Notable for introducing the conspiracy-prone Lone Gunmen, who would become fan favorites and eventually (briefly) have their own spin-off series, "E.B.E." is one of the show's first alien episodes and also one of its scariest.
"Die Hand Die Verletzt"
Original air date: January 27, 1995
A key scene from "Die Hand Die Verletzt" 
Ritualistic sacrifices and demonic substitute teachers plague a suburban high school in this underrated but very unnerving season two outing. For X-Files fans, the moody and atmospheric "Die Hand Die Verletzt" established early on the brand of "horror" that the series endeavored to deliver. Here, the show's dreary Canadian production values are an asset here, helping contribute to some of The X-Files' most unsettling imagery and music — especially during a climactic sequence that intercuts between harrowing storylines before culminating with (literally) one hell of a shocker ending.
"Humbug"
Original air date: March 31, 1995
A key scene from "Humbug"
Darin Morgan announced himself as the most singular voice in the canon of X-Files writers (something he continued through the revival series) with his inaugural episode, "Humbug." While Morgan had a "story by" credit on an earlier episode, ultimately written by his brother Glen Morgan and James Wong, this was his first standalone script. And what a script it is.
"Humbug" sends Mulder and Scully to a town built by, and home to, carnival performers (some might refer to them as "sideshow freaks"), where a series of murders have left the residents — and, indeed, the F.B.I. agents — utterly baffled. Full of fine supporting performances from Jim Rose, Michael Anderson (in perhaps the most overt of the many Twin Peaks parallels) and the late Vincent Schiavelli, along with Morgan's patented mixture of the sublime and deeply silly, "Humbug" is an especially formative hour for the series.
"Clyde Bruckman's Final Repose"
Original air date: October 13, 1995
Peter Boyle, Duchovny and Anderson in a scene from "Clyde Bruckman's Final Repose."
This was the second script turned in by revered writer Darin Morgan, and it cemented his status as one of the show's go-to scribes for "outside-the-box" entries. This Emmy-winning episode is centered around the titular character (beautifully played by the late Peter Boyle), a man who has a unique ability: he can see into the future and knows how everyone dies. Eventually he's put in the crosshairs of a murderous psychic, leaving Mulder and Scully to serve as his security detail.
One of the more macabre and hilarious episodes of the series, "Clyde Bruckman" is also one of the show's most moving. The episode won both Morgan and Boyle Emmys, which was remarkable given how early into the show's run the episode was. But when it comes to "Clyde Bruckman," Academy voters were clearly enchanted.
"Home"
Original air date: October 11, 1996
A scene from "Home"
An episode so intense that Fox threatened to never air it again (they did, of course, and it can be streamed any old time you want), "Home" is certainly one of the series' most terrifying episodes — and one of its most memorable.
Written by the renowned team of Glen Morgan and James Wong, Mulder and Scully travel to Home, Pennsylvania, to look into the discovery of a discarded, horribly deformed baby corpse. (When an episode starts with a baby corpse, you know it's going to be bleak.)
Eventually, the agents stumble upon the Peacocks — a family of inbred, murderous mutants who make the Texas Chainsaw Massacre clan seem like Care Bears. There are so many unforgettable moments from this episode, including one of the series' most brutal murders ever, set to the cheery strains of Johnny Mathis' "Wonderful! Wonderful!," and the hour's tone is so pervasive and atmospheric, it will leave an indelible mark.
"Bad Blood"
Original air date: February 22, 1998
"Bad Blood" (above) was written by Vince Gilligan.
Mulder and Scully constantly have opposing points of view, sometimes on the same event that they both experienced. But what "Bad Blood" does so brilliantly, thanks to a masterful script by Vince Gilligan, is actually dramatize those opposing views. The agents each recount an investigation into a potential vampire situation, with wildly different perspectives. (Gilligan claims it was inspired by an episode of The Dick Van Dyke Show, when Rob and Laura have differing points of view on a fight.)
The results are both unsettling and hilarious, with Luke Wilson putting in an incredibly elastic performance as a small town sheriff (and potential vampire). Wilson also starred in Home Fries that same year, a movie written by Gilligan. "Bad Blood" is one of the rare non-Darin Morgan comedy episodes of the series that was actually funny. It's become a cult classic for good reason.
"Drive"
Original air date: November 15, 1998
Bryan Cranston and Duchovny in a scene from "Drive."
While "Drive" is perhaps best remembered for putting Bryan Cranston on writer Gilligan's radar — something that would pay off years down the line for fans of Breaking Bad — it is also one of The X-Files' most intense hours. In this episode, Cranston plays a man who is convinced that if he isn't careening down the road in a car, his head will explode. (The cold open, one of the show's very best, depicts the same thing happening to his wife.)
The episode's stroke of genius is having Cranston's character kidnap Mulder, leading to a very wild ride. Just remember to buckle your seatbelt before watching.
"Triangle"
Original air date: November 22, 1998
A key scene from "Triangle," directed by Chris Carter.
The X-Files creator Chris Carter, who helped bring most of the show's memorable alien conspiracy episodes to life, took a break from the overall series mythology with the fan-favorite "Triangle." Here, as writer and director, Carter simultaneously riffs on time travel, the Bermuda Triangle and Alfred Hitchcock's Rope, with the episode (about a haunted cruise ship shifting backward and forward from World War II to today) featuring cast members playing different characters. It's a total romp, and one of the most enjoyable hours the series ever produced.
10. "Roadrunners"
Original air date: November 26, 2000
A scene from "Roadrunners"
The only post-Mulder episode on this list, "Roadrunners" was one of the installments that saw Scully partnered with Agent Doggett (Robert Patrick). For those curious, this episode exists in the window of time after Duchovny left but before Anderson would also decamp (replaced by Agent Reyes, played by Annabeth Gish).
Scully and Doggett investigate a dusty backwoods community where a cult worships an evil unknown — a giant parasitic slug. Somehow, it's even grosser and more unsettling than that description, with Vince Gilligan working overtime to creep you out.
The X-Files is now streaming on Hulu.
