Gillette's 1899 stage play is one of the first prominent Sherlock Holmes adaptations, and it was turned into a film in 1916 (on youtube here) with all the same actors. It's kind of funny adaptation, though the cards are somewhat stacked against it because it's translating a stage play that's by necessity mostly dialogue, to a silent movie that's by necessity mostly not dialogue.
The plot feels like a slightly incoherent prototype for a very Hollywood take on Sherlock Holmes: of course it's got Moriarty as essentially a mob boss, though he doesn't really accomplish anything, and there's a character based on Irene Alder, who of course is Holmes's love interest. Watson is mostly relegated to a fun cameo, and Holmes himself feels a bit like an early action hero at times with how seriously he takes everything.
I appreciate that they at least renamed the Irene Adler expy to Alice Faulkner, because she's only really vaguely inspired by Irene Adler. Presumably to make her a more "suitable" love interest, it's Alice's sister who had a relationship with the Prince and then tragically died of a broken heart. Then, presumably to make Holmes look more heroic in comparison, some con artists are also after her sister's letters to the Prince and hold Alice against her will.
However, they clearly felt they had to keep Holmes's trick of using a fire to get Irene Adler to reveal where the portrait is hidden, so Holmes fakes a fire instead of actually rescuing Alice from the con artists, even though he knows she's being held against her will, which feels as strange as it sounds, especially when they go out of their way to make him a gentleman about the letters after he finds them.
Then, at the end, Holmes again reluctantly tricks Alice into giving up her letters to the Prince, even though part of the point of the original story was that the Prince was in the wrong and that Irene Adler deserved to keep her photograph. It's not clear why Alice's case is any different, especially since this is immediately followed by a romantic moment between Holmes and Alice, which would have made way more sense if he had nobly decided to turn away the Prince, earning her trust.
Moriarty's role is just as strange; though he gets a lot of screen time, he doesn't really effect much. He visits Holmes, like in the The Final Problem, but even he doesn't seem to know what he's trying to accomplish with the visit. There's a long sequence about setting up a death trap that the heroes never even end up being threatened with. And he's finally defeated because he disguises himself as a cabby so that Holmes can catch him by asking for help with his bags, like at the end of A Study in Scarlet, which doesn't really make sense out of context.
It tried to do a bit of everything and as a result, it felt like they did none of it terribly well. I'm mostly left with a feeling of relief that this adaptation didn't eclipse the original, as prominent early adaptations sometimes do. In fact, it seems like subsequent movies supposedly based on the play were increasingly loose with it, to the point that Alice is given an original love interest instead of Holmes in the 1939 Rathbone film, almost bringing us full circle back to Irene Adler's marriage to Godfrey Norton in the original story.
