For better or worse, The Imaginarium of Doctor Parnassus will be known more for being Heath Ledger's last film than for anything else.

The latest film from Terry Gilliam came close to being shut down outright after Ledger's untimely death from an accidental overdose. But with some clever script changes, and with the help of Ledger's peers, production on the film proceeded.

Eighteen months later, we're finally able to see the final performance from the brilliant young Ledger.

As with The Dark Knight, in which Ledger created a chilling Joker, his performance in Imaginarium is original and convincing. He seems at ease in the role of Tony, a charming and charmed charlatan on the run.

Unlike the Batman film, though, the magic of Imaginarium does not begin and end with Ledger's performance. This film required beautiful acting from an ensemble and Christopher Plummer, Lily Cole, Andrew Garfield, Verne Troyer and Tom Waits all stole the film at various points.

Plummer's Doctor Parnassus, infused with Shakespeare's Lear, is at once immortal and frail, full of fury and power. He's kept in check, and mostly on track, by his fool, the dwarf Percy, played by Troyer with a cool resolve.

Parnassus, a former monk in charge of the monastery responsible for telling the "eternal story", has been locked in an eternity of wagers with Waits' trickster devil, Mr. Nick, over the collection of souls.

Gilliam's fairy tale thus sets up the simple conflict between light and dark over humanity's choice. Mr. Nick encourages the temptations of the body, while Parnassus is all about the power of imagination, the inspiration of spirit. He's a story teller, after all.

We are introduced to the Doctor and his company of players — his daughter Valentina (Cole), the assistant who is smitten with her, Anton (Garfield), and Percy — late one night outside a London nightclub. The small, troupe travels around the city in a wagon, staging dated and awkward performances and inviting audience members to step through a mirror on stage.

Mirrors have long been portrayed as portals to other worlds, and the mirror that is centre stage in the Parnassus sideshow is a portal to the mind of the Doctor, the imaginarium where he gives people an opportunity to make their choice.

These dreamscapes, bizarre and sublime, are a perfect way to show off Gilliam's imagination. The director was a member of the Monty Python troupe and was responsible for the brilliant interstitial cut-up sequences that featured things like massive feet squishing disembodied heads and squawking babies popping out of drawings of a singing Queen Victoria.

This talent of Gilliam's, the ability to compose melanges of images, to juxtapose crazy, craft-like art in absurdity, is why he's such a wonderful fairy tale teller, and why the best of his films find a way to leverage this skill of his.

It's a dark time for the Parnassus company, though, as Valentina's sixteenth birthday is just days away, and on that day she'll become the property of Mr. Nick because of a wager between the devil and Parnassus years before. Of course, Valentina doens't know any of this, and Anton is only interested in helping her to run away to live the normal life she dreams of.

Enter Tony, a man who claims to have lost his memory in an attack that nearly took his life. The troupe rescues Tony from being hanged and put him to work as a player. He's a natural at it, of course, entirely comfortable stepping into a new role. He proves to be a boon as Parnassus works to collect souls in yet another gamble by the ancient man to save his daughter's soul.

Parnassus believes that Tony could be their salvation, and calls him a man of destiny. Certainly he's a modernizing force for the sideshow, but things go awry when the Russian mobsters that tried to hang Tony stumble onto the sideshow and chase him through the mirror. This is when Tony's face changes, three times, as his true nature is revealed.

The three actors who stepped in to play incarnations of Tony after Ledger's death are all excellent, but only Johnny Depp was able to imbue the character with his own spirit while staying true to what Ledger had already created. That said, Jude Law and Colin Farrell were perfect choices to play the particular "faces" of Tony they took on. Law the wide-eyed romantic and Farrell the suave but dangerous fox.

The problems with Imaginarium come at the end. The social commentary — about the use of children as beacons for questionable motives — becomes a little too heavy handed in the sequence when we learn the truth of Tony.

And the plot becomes a jumble when the entire ensemble ends up in one of Parnassus' dreamscapes, and it is entirely unclear as to who's imagination is in control, and whose choice is important. This means that the wager between Mr. Nick and Parnassus is unresolved. But that is perfectly acceptable, because Mr. Nick makes it clear that he's less interested in winning than he is in maintaining the wager, the strange relationship with Parnassus.

What is also acceptable is that everybody seems to get what they deserve.

Which is how all fairy tales should end.