Universal Pictures' long-discussed plans for a shared cinematic universe reviving its classic movie monsters got off to a shaky start in with The Mummy, which arrived in June to negative reviews and a disappointing worldwide box office of $397.6 million. Now Alex Kurtzman, the film's director and one of the architects of the Dark Universe, is casting doubt on his own future with the franchise.

RELATED: Enough With Cinematic Universes -- Just Make Good Movies!

Asked whether he's still involved with the Dark Universe, Kurtzman told IGN, "You know the truth is, I don't know. I really don't know. I haven't really decided is the honest answer."

A veteran writer and producer whose credits include Transformers, Star Trek and The Amazing Spider-Man 2, Kurtzman was tasked, along with Chris Morgan (the Fast and the Furious franchise) to shepherd the Dark Universe; they're expected to produce 2019's Bride of Frankenstein, from Beauty and the Beast director Bill Condon. However, now Kurtzman is saying, "I have to stay interested in it. I have to feel like my passion is there for it."

RELATED: Tom Cruise's Creative Control May Have Unraveled The Mummy

Starring Tom Cruise, Annabelle Wallis, Sofia Boutella, Jake Johnson, Courtney B. Vance and Russell Crowe, The Mummy grossed just $74.5 million domestically on an estimated $125 million production budget. One positive that could keep the Dark Universe afloat is that the film performed well overseas. Still, Universal hopes to be able to tap into the domestic audience next time around. "I think every movie will be different," Kurtzman said. "I certainly know that the legacy of the monsters have endured across the world throughout the years. Almost a century. So I have to believe American audiences will find it too with the right ingredients."

In addition to The Mummy and the Bride of Frankenstein, the Dark Universe is also slated to include a Creature from the Black Lagoon entry, as well as films centered around the Invisible Man, Van Helsing, Wolf Man, Frankenstein, Dracula, Phantom of the Opera and the Hunchback of Notre Dame.