An unreliable narrator is an interesting storytelling device. But Fox’s “Legion,” which premiered Feb. 8, takes that idea to an extreme — with an unreliable reality.

“Legion” is the story of 20-something David Haller (Dan Stevens) who, unfortunately, is an inmate of a psychiatric institute. As the story progresses, various flashbacks show that Haller sees and hears things that aren’t there. He spends his time in the day room waiting for meals and medication with a chatterbox girl named Lenny (Aubrey Plaza), whose upbeat personality belies her drug and alcohol addictions. Then arrives a girl named Sydney Barrett (Rachel Keller), with whom Haller is immediately smitten. Despite a fear of being touched — presumably haphephobia is why she is institutionalized — Syd agrees to be Haller’s girlfriend.

But when they do touch (a kiss, actually), something very strange happens. Well, more than strange. Violent. Inexplicable. And pretty lethal for just about everyone around them.

Yes, it’s a superhero show. Don’t look for capes and tights, though, because you won’t find any. As Marvel’s Stan Lee proved in the 1960s, “superhero” isn’t a genre, but a vehicle for telling all kinds of stories.

“Legion” is based on a character from Marvel’s X-Men line of books (the word “mutant” was probably a tip-off) who is the son of Charles “Professor X” Xavier and a woman he had an affair with before he formed the X-Men. In both the comics and movies, Xavier had the most powerful mutant mind on Earth.

Until David Haller was introduced, that is, in 1985. Haller was so powerful he could reshape reality with his mind. The catch was that he was caught in a terrorist attack while still a young boy, which activated his powers prematurely — killing all the terrorists, but absorbing many of the minds present into his own. That resulted in dissociative identity disorder. It also left him catatonic.

It got worse when he woke up in his 20s, because his psyche was fractured, and each of the personalities in his head manifested his psionic ability as a different superpower.

Haller had a lot of adventures in various comics, from “New Mutants” to “X-Men: Legacy,” each more bizarre than the last. For the most part, he was usually the villain of the piece, as one personality or another started wreaking havoc and various configurations of X-Men would rise to stop him. Many such stories took place entirely on the psychic plane — in Haller’s mind, that is — and a couple of them resulted in his death.

Yeah, death. But he’d get better. He does, after all, have a lot of different “lives” to play with.

Not that any of this is significant for the TV show, which uses the Legion stories in the comics as inspiration more than holy writ. The show is nominally connected to the “X-Men” film series, at least in spirit, but I wouldn’t expect Deadpool or Wolverine to drop in for a visit.