After a period of story structure and relative coherence with The Fisher King, Twelve Monkeys and Fear and Loathing in Las Vegas, Monty Python alum Terry Gilliam returns to his whimsical ways with The Imaginarium of Doctor Parnassus. The bittersweet film also serves the unfortunate double-duty of being a memorial to Heath Ledger, as it was his last project before his death. Also unfortunate is the result of Gilliam’s effort, which is a bit of a mess and–worse–a bore.

Dr. Parnassus (Christopher Plummer) and his two-man, one-woman show perform their vaudeville-ish act from a horse-drawn carriage in the modern streets of London. Unbeknownst to his sparse audiences is the fact that he was once immortal, a reward he won from a wager with the devil. He lost that immortality later in another Satanic bet. The price for his loss: he must give up his daughter to Lucifer on her sixteenth birthday.

One night the small troupe comes upon a young man hanging from a noose. His name is Tony (Ledger) and he’s an amnesiac. He joins their little carnival just in time for Dr. Parnassus to take the devil up on one last bet. Episodic hijinks of the through-the-looking-glass variety ensue.

Since Ledger died during the film’s production, Gilliam recruited Johnny Depp, Jude Law, and Colin Farrell to play different “versions” of Tony. The justifications for these radical changes in appearance make enough sense for what is in the script, and the trio of actors perform admirably, but the knowledge of the reasoning behind the casting can’t help but make it feel like an exaggerated device and, occasionally, a gimmicky stunt to salvage the movie.

Ledger’s swan song is admirable but not especially memorable. This isn’t the type of film to showcase performances, though; the entire cast is simply in service to the material.

By now, it’s no secret that the indulgent Gilliam’s first and foremost concern is special effects for his flights of fantasy. While impressive, the expectedly surreal imagery is nothing we haven’t seen before from the man who brought us Brazil. It’s always nice to see giant, floating day-glo jellyfish, but it’s even better if they were in a movie with a deeper point than “Nothing is permanent, not even death.”

The director’s recurring fondness for little people is here as well, with Verne Troyer as the doc’s sidekick.

Overshadowing the effects, and Ledger, is singer Tom Waits as the mysterious Mr. Nick–better known as Satan. With a pencil-thin mustache, Ron Perlman smirk, and that glorious voice of gravel, his version of Mephistopheles is the most impressive thing on the screen. No easy feat considering all the extra baggage loaded into the film. His scenes carry an uneasy, edgy charge that should have been felt throughout the rest of the film.

As of now, The Imaginarium of Doctor Parnassus serves as a memorial to Heath Ledger. In future years, though, like The Adventures of Baron Munchausen, it will likely be regarded as one of the auteur’s more impressive misfires.