TV legacies are funny things. TV fans, too. By the time “Twin Peaks” was quietly laid to rest on June 10, 1991, “Murder, She Wrote” was the top-rated drama on television. “Peaks” was poised to disappear without a trace.

Fast forward to today. “Murder,” a perfectly fine procedural that starred the glorious Angela Lansbury, is mostly forgotten. “Twin Peaks,” by industry consensus, is one of the most influential series in TV history.

How could this have happened? Why? And on the subject of baffling cosmic questions, this: Whatever happened to coffee-swilling, cherry-pie-loving FBI agent by-way-of-Mayberry Dale Cooper (Kyle MacLachlan)?

In a few short hours, some answers.

Maybe.

When that mythical and once-thought-unobtainable “third season” arrives on Showtime Sunday night, no one will dismiss it as just another retread or do-over. For a quarter century, fans held tightly to the dream of a revival. So have co-creators David Lynch and Mark Frost. Both have talked about “unfinished business” — code for the bitter break with ABC and the disappointing second season all those years ago.

Other than a few vague trailers, Showtime execs have said almost nothing about the 18-episode revival and even declined to send out episodes for review. There remains the possibility that Showtime doesn’t have a clue what the series is about — ABC never did, after all — but more likely this is a Lynch dictate. He has his reasons, and, as always, they are mysterious.

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Another mystery is the cast. In one concession to publicity, Lynch released the full list — an astounding roll call that went on for 217 names and includes stars as diverse as Laura Dern (reportedly in a major role) and Jim Belushi (maybe not so major). Most of the original cast is returning, but several iconic ones are not, notably Michael Ontkean as stoic sheriff Harry S. Truman. Michael J. Anderson, the famed backwards-talking “Man from Another Place,” was not on the list, either.

Then there’s this puzzle: Frank Silva — who played the evil spirit “Bob,” who evidently occupied the body of Cooper in the closing seconds of the series — died in 1995. Unless Lynch plans to CGI-revive him, much as “Star Wars: Rogue One” did Peter Cushing’s Grand Moff Tarkin, then this revival has at least one other major hurdle ahead.

Why is all this such a huge deal now? A bit of history is in order:

Back in 1990, Lynch arrived at ABC with a cult movie following and an outsized rep for innovation that had paid off (“Blue Velvet”) and not (“Dune”). But the also-ran network needed to take risks, and “Peaks” seemed like a good one.

Superficially, “Peaks” seemed at first like a murder mystery. The series opened April 8, 1990, with the discovery of a body wrapped in plastic on a rocky beach near the fictional town of Twin Peaks, Washington. “She’s dead,” wailed Pete Martell, played by Jack Nance, who had helped launch Lynch’s career as Harry Spencer in 1977’s cult classic “Eraserhead.” He put a call into the cops. Sheriff Truman and his deputy, Andy Brennan (Harry Goaz), investigated. At the scene, Andy — who didn’t know the victim, homecoming queen Laura Palmer — cried uncontrollably.

Viewers knew they had entered terra incognita. They were about to find out just how incognita.

“Peaks” was funny, but also bizarre. A minimalist score by Angelo Badalamenti seemed to fuse cool-cat jazz with Philip Glass, and synth-pop with a funeral dirge. A long, low wail in a minor key often tracked for minutes on end. Something very bad was always about to happen. But what?

The characters were eccentric, perhaps none more than FBI agent Dale Cooper, a Boy Scout with a fondness for coffee “black as midnight on a cloudless night.” Lynch blew Cooper’s mind — and viewers’ minds, too — by the third episode in what is now widely considered one of the most influential sequences in TV history: Dale has a dream in which Laura (Sheryl Lee) comes to him, and a little person, the Man from Another Place, sings: “Let’s rock! I’ve got news that the gum you like is going to come back in style . . . ”

The episode was spectacular. Also inscrutable. From that point on, “Peaks” unfolded like a procedural on acid. Viewers peeled away. ABC got nervous, and then did what nervous networks always do: Interfered.

“Peaks” got a second season, with conditions. ABC wanted Laura’s killer revealed. Lynch did not. It wanted coherent storytelling, with an ongoing teen love story. The season aired for a full 22 episodes, but the demands of commercial TV proved too much. Lynch stepped away, returning to direct the glorious finale, which blew the remaining viewers’ minds all over again. It didn’t matter. “Peaks” was canceled anyway. Lynch directed the movie prequel “Twin Peaks: Fire Walk with Me” the following year, but the culture had moved on.

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“Peaks” seemed done, except for the fact that some fans weren’t. A few realized that the show could be subjected to something called “hermeneutic” analysis, much as great works of literature could be. They explored the symbols, delved into the meanings, even launched a well-regarded magazine, “Wrapped in Plastic.”

In time, “Peaks” would be seen as prophetic. With a few magnificent exceptions (“The Twilight Zone,” “Star Trek”), the prime-time TV drama had always been about certitude. There was a beginning, middle and end. Stories made sense. They didn’t explore the subconscious through symbols. Surrealism was unacceptable.

TV execs reasonably assumed viewers wanted order. What they never anticipated is that millions of viewers wanted this too. “The Sopranos,” “Lost,” “Breaking Bad,” “Mad Men,” and every 21st century drama that tweaked its nose at tired prime-time conventions owes its existence to “Twin Peaks.”

And now we’ve all come full circle. Lynch, who always declined to analyze the meaning of his own work, has 18 more hours to finally fulfill his legacy.

Maybe “Twin Peaks” was about everything. Maybe it was about nothing.

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It doesn’t matter. We’ll still watch.