The Imaginarium of Doctor Parnassus
(Terry Gilliam) Heath Ledger, Johnny Depp, Colin Farrell, Jude Law, Christopher Plummer, Lily Cole, Tom Waits, Andrew Garfield
Running time: 122 minutes (12A)
Rating: 2.5/5

ROLL up! Roll up! The imaginarium of Terry Gilliam is in town. Experience the wonders of his wacky imagination, the spiralling fantasy that knows no bounds. Meet Dr Parnassus, a 1,000-year-old man (Christopher Plummer) who lives immortal. He could be another incarnation of God and spends his days locked in battle with the Devil (Tom Waits) for human souls. Travel with him and his Victorian theatrical troupe, who ride horse-drawn through modern-day London in darkly-lit streets on a travelling stage two storeys high. Watch as they entice on stage drunken revellers, who step through a mirror into their own imaginations where their choice of path determines the taker of their soul. Travel through the mindscape of these individuals, where – in the hands of Gilliam – anything could happen. And be amazed at the silliness of it all. And wait: there's one last treat, the one you've all been waiting for. Drum roll please for the final performance of the late, sadly departed Heath Ledger.

It's difficult not to feel a twist in the gut at the first sighting of Ledger: London is lit in Gothic doom like it's the 1800s and there's Ledger's Tony, dangling by his neck off a rope under a Thames bridge. Mysteriously, he's still alive and is rescued by two of Parnassus' troupe: sleight-of-hand expert Anton (Andrew Garfield) and Parnassus' daughter Valentina, whom Anton has a crush on, which is not surprising really, considering she takes the shape of the supermodel Lily Cole, whose face is as milky as the moon. Tony is a mystery: he comes ponytailed in a dirty white suit with a haggard face and strange markings on his forehead.

He claims to have no memory and joins the troupe. Later he will learn of a deal for Valentina's soul between Parnassus and Old Nick, and the plot pivots on what he will do about it.

Another mystery is Ledger's take on the role. In The Dark Knight, he went wild: that film, told straight and sharp, allowed him to dial The Joker up into exuberance – a one-man carnival. Here, he is battling with the carnival that is Gilliam's film style and you sense Ledger didn't know how to modulate it: large or small, quiet or loud? He mumbles like Brando, growls like The Joker and dandies like Depp. But his Tony never settles.

Ledger's death mid-shoot left Gilliam in a serious pickle. The solution is diluted clever. When Ledger's Tony steps through the stage mirror, he emerges into Gilliam's hallucinatory world with similar pony-tail and goatee, but with the face of Johnny Depp. And for five minutes, the film comes fully alive. Depp's eyes glitter, his mouth twitches and that dandy Keith Richards tone curls duplicitously. Depp is a dab hand in the realms of the fantastical and you get a sense immediately of the perfidious nature of Tony's character. Depp is a charm, effortlessly in control, and he makes Ledger look like a warm-up act.

The next time Tony steps through the mirror, he emerges with the chiselled mug and piercing eyes of Jude Law. Later still, he turns into Colin Farrell. You start to think some guys get all the luck. But then you see the performances: Law's face is set in a permanent rictus of clueless desperation, while Farrell struggles to make anything of Tony as the film rides out the endgame of the last reel. Perhaps it's too much of an ask to inhabit a character that's been played already by three different actors. Though I suspect this is not really Farrell's fault.

The Imaginarium of Doctor Parnassus, stuck somewhere in an acid trip between Faust and The Adventures of Baron Munchausen, is a sickly confection of the silly. It's undone by its excess of imagination at the expense of any credible storyline. Gilliam throws everything into the pot: his genius for creating delirious fantasies is never in doubt. Law staggers about on top of hundred-foot stilts in a world that looks like Monty Python meets the Yellow Submarine, while Farrell's Tony rides a river in a gondola in a countryside like melted sweets. But the story is as thin and flimsy as an old pop-up book. Tom Waits' smooth cat of a Devil is pure pantomime and the characters never feel like they're in jeopardy.

Earlier in the film, Anton magically creates a chicken mid-air in front of a crowd and nobody notices. Parnassus grumbles that people today have lost their imagination. Gilliam, with his propensity for the outlandish, may well feel like that. But nobody is going to care too much unless you've got a cracking story to tell, no matter how loudly you paint it.