“The last two weeks have been a box office bloodbath,” Exhibitor Relations box-office analyst Jeff Bock tells The Hollywood Reporter, and he’s not wrong. With every weekend of the month giving us a new, high-profile flop or disappointment, and the same handful of movies topping the box office week after week, it’s been a mighty grim October. But the Halloween weekend marked the lowest total box office of the year — even lower than that first weekend in September that was topped by that “faith-based” movie you still haven’t heard of.

The most high-profile failure of this particular weekend was David Gordon Green’s actually-pretty-good Sandra Bullock vehicle Our Brand Is Crisis, which not only ended a monster of a commercial winning streak for Ms. Bullock (Minions, Gravity, The Heat), but marked her lowest wide-release debut ever, its (gulp) $3.4 million opening even undercutting (double-gulp) her 1996 Denis Leary pairing Two If By Sea. Bradley Cooper’s strangely familiar Burnt barely performed better, coming in fifth place with $5 million. The top four was comprised entirely of holdovers: The Martian, Goosebumps, Bridge of Spies, and Hotel Transylvania 2.

So what happened? Well…

1. I’m not sure anyone predicted the extraordinary success and staying power of The Martian ($182 million domestic, $428 million worldwide, soon to become director Ridley Scott’s biggest domestic earner to date), a movie that seems to have locked in with all quadrants: men and women, genre fans, young moviegoers, bookworms, and adult audiences looking for brainy fare. Its word-of-mouth value is off the charts, and people are going to see it on recommendations from friends rather than taking a chance on newer fare. And in spite of its strangely low-key marketing, Bridge of Spies is a hit with older audiences, for whom its combination of Spielberg, Hanks, and Cold War storytelling is total catnip. And that’s an audience that keeps talking and keeps coming to the theater, as evidenced by its slender week-to-week drop-offs.

2. As far as the short term goes, horror fans were wildly underserved this Halloween weekend. The only wide releases targeted anywhere near them were Paramount’s Scouts Guide to the Apocalypse and Paranormal Activity: The Ghost Dimension — which both played in significantly fewer theaters thanks to their collapsed theatrical-to-home window — as well as Crimson Peak , which hardcore horror fans quickly learned was more of a Gothic romance than a blood-spiller.

3. It just got too damn crowded. Our Brand’s commercial failure is easy to pinpoint: this was a movie that needed great reviews to get its audience out to the theaters (particularly on a weekend when the parents among them were otherwise occupied), and those reviews were not forthcoming. But the films it joins on the October trash heap are telling: Steve Jobs, The Walk, Rock the Kasbah, and the aforementioned Crimson Peak were all intended for an adult audience that didn’t show up, choosing instead to keep boosting The Martian and Bridge of Spies.

Part of this is simple programming: conventional wisdom holds that adult-oriented movies can only perform in the fall, so we end up with a glut of them, and October becomes as competitive for prestige pics as June is for blockbusters. And part of the problem is, admittedly, quality — not all of these were great movies, and a couple weren’t even terribly good. But it’s certainly refreshing to have them as options rather than yet another sequel, adaptation, or reboot.

What’s worrisome is that this is going to be the takeaway from the October Bloodbath: not the equally loud belly-flops of bloated fairy-tale origin story Pan or kitsch cartoon adaptation Jem and the Holograms, but the underperformance of challenging pictures like Steve Jobs and Crimson Peak. It may stand to reason that the grown-up audience Hollywood ignores the rest of the year is a no-show in fall too. And the implications of that are very grim indeed.