Kevin Costner mortgaged his home and put $38 million of his own money into “Horizon.” Box-office numbers suggest this was a terrible idea.

But so far, Costner’s gambit on the movie he directed, cowrote, and stars in hasn’t paid off: “Horizon: An American Saga” brought in only $11 million on a $100 million budget in its opening weekend.

This isn’t the first time Costner has had a passion project go sideways. He produced, starred in, and later took over directing duties in 1995’s “Waterworld,” an ambitious postapocalyptic blockbuster described as “Mad Max” on water. He sank $22 million of his own money into the film, which was then considered one of the most expensive movies ever made. When critics saw it, they also gave it the distinction of being one of the worst movies ever made.

But “Horizon” was supposed to be different. The Oscar-winner had been riding high off the success of his hit TV show, “Yellowstone.” Surely its tens of millions of fans would follow Costner to theaters to watch him in another Western, one he directed this time. Right?

At least on opening weekend, that’s not what happened. Audiences instead spent their cash on sure things, like sequels or stories from existing IP. “Inside Out 2” led the domestic box office for a third straight weekend and has now grossed over $1 billion worldwide, making it the first movie to do so since last summer’s “Barbie.” In second was “A Quiet Place: Day One,” a prequel in the popular thriller franchise, which took in an impressive $53 million domestically, making it the biggest opening ever for the franchise.

The “Yellowstone” fans weren’t enough

Though Costner had been crafting a story about the exploration of the American West for decades, it wasn’t until he played John Dutton in “Yellowstone” that “Horizon” finally became a reality. And it was that fandom that Warner Bros. hoped would come to theaters for “Horizon,” bringing box-office glory.

The Paramount+ series was the most-watched cable series in 2018 and 2019; it went on to score close to seven million viewers in its broadcast debut on CBS in the fall of 2023. The conventional thinking among box-office trackers was that “Yellowstone” fans would be the core audience to come out to support “Horizon,” hopefully leading to a $15 million to $20 million opening.

Despite the film’s poor reception from critics at its Cannes Film Festival world premiere and its 40% Rotten Tomatoes score, the thinking was that Costner’s core audience would come through despite a few bad reviews (the movie has a 71% audience score, after all).

And they did — sort of. Warner Bros.’ weekly box-office report revealed that the top five theaters that were major earners for “Horizon” were in regions of the country where “Yellowstone” is popular and cowboys still roam: Utah (where the “Horizon” franchise was shot), Texas, Arizona, and Oklahoma.

So, while Costner and WB were successful in marketing the movie, it wasn’t enough. Though the “Yellowstone” fans are mighty, “Horizon” needed more manpower to compete with established draws like “Inside Out 2” and “A Quiet Place: Day One.”

Costner isn’t as prominent in the 3-hour movie as marketing would suggest

Even though “Horizon” needed more than just “Yellowstone” die-hards to win at the box office, that core audience may not have been entirely satisfied, either.

Despite being the face of the franchise and its star, Kevin Costner isn’t actually in a lot of “Horizon.” In fact, he doesn’t show up until an hour into the movie and is rarely seen afterward. As Hayes Ellison, a rustler on the run after killing a man, the movie occasionally checks in on how he’s doing, but most of it revolves around Native Americans attacking a settlement called Horizon, the soldiers at a nearby Army post, and a wagon train traveling to Horizon.

The movie’s lack of Costner is a major flaw. Unlike on TV, where teasing the eventual appearance of a star will draw audiences back for the next episode, it’s tougher for movies to take that approach when viewers must wait more than a week — usually months or even years — for the next installment. And even though the next “Horizon” movie comes to theaters in August, who’s to say audiences will come back? Especially if they aren’t certain their star will be on screen for most of the movie.

Self-financed auteur projects rarely deliver

The shaky start for Costner’s passion project could go one of two ways. While there are a few times in film history when a director put their own money into a film and reaped huge rewards (see: George Lucas’ “Star Wars: The Empire Strikes Back,” Mel Gibson’s “The Passion of the Christ”), most of the time, directors who self-finance never see that money back — just ask Orson Welles or Francis Ford Coppola.

It’s too soon to say if that will happen to Costner (even “Waterworld” broke even — though it took years), but he is on the hook for the film franchise, and he’s likely in deeper than the $38 million price tag that’s been previously reported.

According to Variety, Costner and his investors are paying for the “Horizon” marketing, a spend that’s around $30 million. Warner Bros. is only taking 8% of the movie’s box office grosses. That means if the movie can rebound, the star will take a substantial share of the grosses. If it doesn’t, he’ll have to deal with the losses.

That could hurt the franchise down the line.

Though “Horizon: Chapter 2” is set for an August 16 release and “Chapter 3” has begun principal photography for a May 2024 release, “Chapter 4” is still only in development. Whether Costner will ultimately be able to complete his four-part saga could very well become a saga of its own.