This article originally appeared on VICE US.

Twenty-five years ago, a pragmatic Catholic redhead working at the FBI was ordered to covertly observe the work of the Bureau's most impractical oddball. Special agent Fox Mulder was a seasoned FBI agent and an expert in behavioral science and violent crime, but by the early 1990s he'd become obsessed with a secret, forgotten collection of cases that involved unexplained phenomena. That’s where Dana Scully found him, alone in a quartered-off, defunct room somewhere in the recesses of the FBI.

The two couldn’t have been less alike. From the moment they met, Scully and Mulder exuded opposite personas: He pored over UFO abduction cases with enthusiasm, throwing pencils into the drop ceiling of his underfunded department, and she was a studied scientist, a forensic pathologist who rivaled Mulder’s eccentricity with resolved skepticism. Though Scully was a plant, positioned beside Mulder in order to document the wastefulness and absurdity of his work, she quickly became his closest ally. Their distinct personalities were the ingredients for a mutually beneficial relationship that could withstand the most dire crises—together they formed a friendship with an unbreakable foundation.

Scully’s cold calculations couldn’t refute that Mulder was on to something—though he was often overly-eager to believe that the unexplained must be paranormal in nature, his instinct to believe that the paranormal was possible proved reasonable to Scully, despite herself. Thus began the dance between two of the most lovable characters in television history. The X-Files was a massive success that continues today (the show rebooted in 2016)—and though the series has taken viewers on a high-octane ride through supernatural storylines that grip our attention, it was the relationship between Scully and Mulder that really kept us watching.

Their friendship did not overcome their differences; it was their differences that drew them closer together. Scully was a scientist with high-powered perception, and she kept Mulder in check, for his willingness to believe often exposed him to harm—especially as the shadowed forces within American intelligence agencies worked to obscure his findings and lead him down false paths as he quested after a very real conspiracy that involved the abduction of his sister.

In turn, Mulder’s dogged pursuit of the truth compelled Scully to look beyond her scalpel and see that some things in this world cannot be easily understood within a rational framework. This realization was something Scully needed desperately, and it was Mulder who helped lead her to it. Though Scully was a disciplined pragmatist, she was also a woman of faith—a faith that wavered or faded, so much so that she lost touch with the possibility of meaning greater than the mortal coil, despite the thin golden cross she always wore around her neck.

Before they'd met each other, Scully had lost her father and Mulder had lost his sister to what he believed to be an alien abduction that was part of a government conspiracy. Throughout the series' nine original seasons, the pair would come closer to understanding their own histories together than they ever could have on their own. Without each other, Scully and Mulder would have been two brilliant minds with beliefs so extreme they blinded themselves from the truths that lay somewhere in-between.

They became each other's closest friends and confidants. And we kept watching, needing to know what would happen to these brilliant, equally handsome and ambitious human beings who were lost in a world of mystery and subterfuge. The alien conspiracy at the heart of the series became a parable of our species' pursuit for self-understanding, and their complementary differences represented a kind of love we aspired toward.

It was only a matter of time until Scully and Mulder's relationship became romantic—but even then, when they lay together in love, it was their friendship that meant more to them, and to us. They never married. Their sexual partnership generally remained somewhere in the background, while their shared mission to expose a massive conspiracy involving extraterrestrials kept steady pace. They weren't always near each other; Mulder disappeared for an entire season. But they were always together in their hearts, saving one another when they needed it the most.