Sherlock Holmes pastiches, whether in print or on film, usually bear a secret label that reads "Caution: Handle with Care." Murder by Decree (1979), one of the better-known film pastiches, is a decidedly odd brew. It takes a premise beloved by pastichers--what would happen if Sherlock Holmes squared off against Jack the Ripper?--and adds liberal dollops of radical anarchism ("in Scotland Yard!" Watson huffs), Freemasons, and misbehaving royals. The final result is a conspiracy theorist's paradise, to be sure, but is it Holmes?
One thing cripples the film from the start: it has a hole where it needs a Holmes. Christopher Plummer's Holmes is strangely soft and squishy, without much in the way of intensity or (dare one say it) basic detective skills. I spent most of my time wondering at Holmes' unbelievable incompetence, which inadvertently leads to the death of two women and one inspector. In many ways, Plummer's Holmes is upstaged by James Mason's fine Dr. Watson; granted, some Nigel Bruce-isms occasionally creep in, but this Watson is appropriately patriotic, protective of his Holmes, and perfectly capable of taking care of himself in a fistfight. Fortunately or unfortunately, Watson also carries out the most significant bit of detective groundwork in the entire film (which leaves Holmes in a most bizarre position).
The plot itself is not entirely coherent, although it draws on the popular legend that the Duke of Clarence may have been responsible for the Ripper killings. Since I'm about to spoil the ending, I'll put the rest of this post below the fold.
Even bearing in mind that this is a thriller, though, it's hard to understand why the government would bother sanctioning the murders of a group of prostitutes in order to cover up Eddy's illicit marriage to (gasp!) a Catholic; as George IV could no doubt have informed the authors (convenient seance permitting, of course), there were easily available solutions to such inconveniences. The film wants to make a deeper point, of course, about the threat to social order posed by both popular discontent and government corruption, although Holmes' speech to that effect doesn't adequately explain how the radical position exactly mirrors the government's. In a manner that is relatively Holmesian, the film concludes that "decency"--and, thus, hope for the future--resides in local resistance to evil, rather than through mass political movements or government control. Holmes spends much of the film accidentally dancing to someone else's tune, undermining his position as an independent force for order who works outside the usual parameters of the law; by the end, he manages to save a child and solve the murders, but he's helpless to unmask the true conspirators. Instead of the Great Detective, we've got the Neutered Detective.
ETA: I forgot to note that the film relies overmuch at times on the stock signifiers of "Holmesness." Violin playing? Check. Allusions to the canon? Check. Watson and the fair sex? Check. Inappropriate use of an Inverness cape and a deerstalker? Check. (The Private Life of Sherlock Holmes took a playful attitude to such things; not so this film.)