His status as a Python and a colourful career as a filmmaker have made Terry Gilliam something of a national treasure.

But it is almost 20 years since he made his last memorable movie, Twelve Monkeys. And the goodwill is wearing thin.

Set in the future, The Zero Theorem stars Christoph Waltz as Qohen Leth, a reclusive loner who lives in a dilapidated chapel and steps reluctantly into the world only to go to work at the Mancom Corporation. There he "crunches entities" alongside other geeky geniuses, though what exactly that means is never explained.

Leth is gripped by a Beckettian existential crisis. Convinced he is about to receive a phone call that will explain the purpose of his life, he begs his manager (David Thewlis) to allow him to work from home so he does not miss it. He is granted his wish on condition he works on the corporation's top secret project, solving the Zero Theorem.

Scriptwriter Pat Rushin is attempting a commentary on faith, technology, marketing, therapy, online sex and the meaning of life - and there is the problem. Gilliam needs a script that keeps him focused. Instead, his storytelling is all over the place, to the point where it becomes plotless and monotonous.

Most surprising is that Gilliam's imagination is so off the mark. In his previous science fiction films, Twelve Monkeys and Brazil, his baroque, retro-futuristic visual sensibility served his conceits; here, we have a Day-Glo, mix-and-match dystopia that never allows us to suspend our disbelief.

There are enjoyable cameos by Matt Damon as Leth's shadowy boss and Tilda Swinton as a virtual therapist. And Waltz gives it everything. But this is Gilliam's fifth middling film in a row. Let's hope his long-cherished project, The Man Who Killed Don Quixote, will break that pattern.