The first 30 minutes of Digger are riveting viewing — funny, dramatic and completely bonkers in equal measure. The film introduces Digger Rockwell, played by Tom Cruise, a phenomenally wealthy and hugely influential oil tycoon who finds himself caught up in a crisis that threatens to spiral far beyond his control.

Cruise clearly relishes the chance to play such an outrageous character. Digger is egotistical, larger-than-life and convinced he is the smartest man in the room, and Cruise attacks the role with enormous energy. Watching one of the world's biggest movie stars as an obscenely wealthy oil baron suddenly confronted by consequences that money can't solve is hugely entertaining.

John Goodman is equally terrific as President Compson, a blustering and politically calculating president whose relationship with Digger provides some of the film's funniest moments. Goodman pushes the character just far enough to make him wonderfully over-the-top without becoming a caricature. Riz Ahmed is also strong as Ganesh, a scientist trying to make the political establishment understand the seriousness of the situation, while Sandra Hüller and Jesse Plemons provide solid support as Emma Rockwell and Kenny.

And then the film takes a very strange turn.

Without revealing any spoilers, the story suddenly becomes considerably more complicated and difficult to follow. What begins as an outrageous and entertaining satire gradually evolves into something far more ambitious and unconventional. Unfortunately, the increasingly convoluted narrative comes at the expense of the sharpness and momentum of the opening, turning what was initially a hugely enjoyable experience into a hard watch.

The performances remain the film's biggest strength. Cruise delivers a flamboyant, committed performance that feels tailor-made for awards season, while Goodman is every bit as good. The two are terrific whenever they share the screen and both could find themselves firmly in the Oscar conversation.

There is no denying Digger's ambition. Alejandro González Iñárritu is clearly attempting something much more substantial than a straightforward disaster movie or political satire. But by the end, the film feels less like a piece of entertainment and more like an elaborate application for an Oscar. The big themes, striking imagery and increasingly complex ideas seem designed to demonstrate importance and artistic ambition rather than simply tell a compelling story.

In the end, Digger is considerably more impressive than entertaining. The opening is riveting, Cruise and Goodman are superb, and there is plenty to admire. But once the story takes its unexpected turn, it becomes increasingly confusing and difficult to engage with.

Cruise and Goodman may well find themselves in the Oscar conversation come award season. Whether Digger itself deserves all the attention it is clearly courting is another question entirely.

For a film that starts with such energy and promise, it ultimately feels less like a great night at the cinema and more like a very expensive, very elaborate Oscar submission.