As sure as “Buffy the Vampire Slayer” was a drama about high school filtered through horror movie trappings like vampires and demons, “Veronica Mars” was a drama about real-life horror show elements – murder, rape, STDs and, most of all, betrayal – filtered through the high-school experience.

“Buffy” and “Veronica Mars” were sisters of the same mother – as a throw-away line in the “Veronica Mars” movie that debuted just this weekend testifies – and are, ultimately, stories about surviving not just people with murderous intentions but the people who love you and the people you love. Betrayal hurts a hell of a lot worse than a stake to the heart or the zap of a Taser.

As TV shows, “Buffy” and “Veronica Mars” ended before their time. Sure, it can be argued that “Buffy” had more weak moments than strong ones in its last couple of seasons, but the most bitter pill for fans is that the show ended before pop culture’s full-on fixation with vampire stories began, with far lesser tales like “Twilight” hogging the spotlight that should have gone to the show that started it all.

And while “Veronica Mars” had the benefit of an online Kickstarter campaign that brought it back as the big-screen incarnation that debuted this weekend, its three seasons – again, admittedly, with some uneven stories late in its run – just missed out on the shared online community of Facebook, Twitter and name-your-social-media that generates – or at least proves to the world – the dedication of fans.

So we come to the new “Veronica Mars,” a big-screen movie that follows up, seven years later, on the heroine who gave the series and movie their names.

Director Rob Thomas, creator of the series, duplicates the success of the series in creating an unlikely protagonist in Veronica: A female protagonist who acts and talks like the tough-guy hero of a hard-boiled detective story but is still, realistically, a young woman trying to navigate the caste system of a small California town.

Neptune – “It really was built on a Hellmouth,” as one character says in the movie, in a nod to “Buffy” – is still a town full of haves and have nots. Thanks to the corruption that rules the town, the haves – politicians and software makers and movie actors and the police who do their bidding – push the have-nots down and keep them down.

Veronica – the former high-school outcast-turned private investigator, still played with toughness and vulnerability by Kristen Bell – returns to Neptune when former antagonist, former boyfriend Logan (charming, as always, Jason Dohring) is accused of killing his girlfriend, a former classmate who’s become a pop celebrity.

The trip means leaving boyfriend Piz (Chris Lowell) and a promising job at a law firm behind in New York. And it means a reunion with friends like Wallace (Percy Daggs III), Mac (Tina Majorino) and Weevil (Francis Capra). There’s also that most dreaded function of “all these years later” plots – an actual high school reunion.

Much more welcome is the reunion between Veronica and her dad, private investigator Keith Mars (Enrico Colantoni). It’s the relationship between Veronica and Keith – heartfelt and quippy, with the warmest and sometimes thorniest parent-child dynamic on TV – that made the show more than a rehash of Nancy and Carson Drew.

Well, that and the more-than-a-little caustic look at a town that seems more relevant today, frankly, than it did in the comparative boom days of the early 2000s. Neptune feels like a jaundiced and corrupt town from the best noir, full of biker gangs, seedy motels and people with either too much to lose or nothing at all.

The heart of the movie is Logan’s dilemma and Veronica’s puzzling out a solution, but there are a lot of nice moments with most of the cast. And there are some nice surprise appearances for fans of the show – mostly along the lines of glimpses of favorite supporting characters, with the notable exception of one who was written out of the story when it was on TV – and a fun and unexpected cameo or two.

The surprises emphasize, in a way, just how focused the movie is on fans – including those tens of thousands who helped fund it through Kickstarter  but also those who fondly remembered the series, its plucky and wry heroine and its jaded look at relationships and a town’s caste system.

The movie’s clubby anti-club slant probably limits its appeal to people who never watched the series. The point of rebooting an old TV show or movie is to bring in new fans, but like the “Serenity” follow-up to Joss Whedon’s “Firefly” series, “Veronica Mars” isn’t likely to engage new followers.

But for the faithful, the fans of the young sleuth and her world, “Veronica Mars” is a welcome reunion.