Parnassus Heights: Terry Gilliam’s imagination is in full flight in film with inspired performances by Heath Ledger, Johnny Depp and Lily Cole.

The Imaginarium of Doctor Parnassus is a patented Terry Gilliam special, a remedial children’s bedtime tale for anxious grown-ups. Gilliam, particularly when he’s collaborating with writer Charles McKeown (Brazil, The Adventures of Baron Munchausen), loves to construct panoramic morality plays with eye-candy visuals, variations on the eternal story of the struggle between good and evil – on a decidedly human scale, of course, despite the grandiose metaphors. Imaginarium fills the screen with Brobdingnagian wonders, yet basically concerns itself with something as humble as the lingering regrets of a poor old carny.

Doctor Parnassus (in a deceptively broad performance by Christopher Plummer) labors under a curse. Many years ago he won a wager with the devil and was granted, or rather sentenced to, eternal life. We meet him and his entourage – daughter Valentina, aka “Scrumpy” (tremulously lovely Lily Cole); Dr. P’s diminutive sidekick Percy (Verne Troyer); and a young actor/gofer named Anton (Andrew Garfield) – in their tattered caravan, moving from place to place in the derelict parts of contemporary London, putting on a curiously old-fashioned magic show for the rubes. They’re constantly pestered by pugnacious drunks, the misapprehensions of ordinary people, and the police, but they persevere. It’s their destiny.

Dr. P can also foresee the future but no one ever believes him. Like a scruffy-bearded Cassandra, he perches immobile in a fake trance (he’s actually drunk) on the caravan’s tiny stage while Anton inveigles passersby to come up, take a chance, and discover their true natures. All they have to do is pass through the Imaginarium, a flimsy-looking “magical mirror.” Dr. P takes care to warn all comers, “What we do is deadly serious,” but no one takes the proposition seriously until it’s too late and the truth is staring them in the face. In the end their minds are purified and so are their wallets, usually.

As he migrates with his troupe, the peripatetic Dr. P carries on a running philosophical debate with his old acquaintance, Mr. Nick. Tom Waits, never better, plays Nick, aka the devil, as a Brecht-ian criminal dandy dripping with lust, in a Mack the Knife getup with his thinning hair dyed a gaudy red and a permanent leer on his face. Somewhere along the way, their latest bet – first one to attract 12 disciples wins – has transmogrified into a quickie soul-scavenging contest. If Parnassus can save five souls from eternal damnation, he gets to retain his daughter Valentina; if Nick suckers five chumps, Val must become the devil’s bride.

This dilemma takes a further histrionic turn when the Parnassus troupe discovers a man in a white suit hanging from a bridge one night. At last, someone more pathetic than any of them. As it turns out, the revived Tony (Heath Ledger) is the tonic that Dr. P’s carnival of souls, and Gilliam’s movie, needed.

The late Ledger left one or two movie roles in the can when he died in 2008, and Imaginarium is now the last to be released. It was in production when Ledger passed away, and substantial scenes had been shot with Tony joining the caravan, scenes too precious to be lost. So Gilliam drew three aces – Johnny Depp, Colin Farrell, and Jude Law, in succession – to portray Tony in the crucial sequences on the other side of the looking glass, the rationale being that when a person enters the Imaginarium, his or her soul can take several forms and even change faces. Voila! Ledger’s farewell part is one of his most poignant, the portrait of a man jerked back to life almost against his will.

Gilliam drenches all this in his most mind-blowing hallucinations since Fear and Loathing in Las Vegas. And yet The Imaginarium contains the requisite germ of sadness and disappointment found in all of the ex-Monty Python’s best work. People are stupid for the most part. Fantastic spectacles cannot disguise loneliness. Even on one of the most hypnotically beautiful moonlit gondola rides in film history (it’s right up there with the moonlit marshland in Sunrise: A Song of Two Humans), love is not a sure thing, ever. The professor cries: “Don’t go through the mirror!” but we can’t help ourselves – it’s in our nature to break on through. Life goes on. The Imaginarium of Doctor Parnassus, one of the very best movies of 2009, hits the road and keeps on going.

THE IMAGINARIUM OF DOCTOR PARNASSUS (4) Directed by Terry Gilliam • Starring Christopher Plummer, Johnny Depp, Colin Farrell, Heath Ledger, Lily Cole and Tom Waits • Rated PG-13 • 122 min • At Century Cinemas Del Monte Center.