Much like Paul Leni's previous mystery/horror, The Cat and the Canary, The Last Warning takes a moderately cliche plot (even for the time) and dresses it up in a way that makes the movie a special and enjoyable treat.
While this film contains some comedic portions (just as The Cat and the Canary did), I feel it's noticeably toned down, and for most of the film, I think the plot's played pretty straight. Which is only a positive, as this mystery, boasting no less than something like ten possible suspects, has a lot of potential from the beginning, and too much comedy would bring it down. Luckily, that didn't happen.
As aforementioned, the cast of this film is rather large, all the more to make the mystery identity of the killer more fun to figure out. It wasn't uncommon to see five, six, as much as ten or eleven, characters all in a single shot. Of course, trying to keep track of everyone throughout the film is close to impossible, but it still helped out the feeling of pandemonium, especially toward the end (during a deeply enjoyable chase sequence).
Laura La Plante (who also starred in The Cat and the Canary) didn't get as much screen-time as you might hope, but still played her character sympathetically (which, given how unlikable she was at the beginning, was sort of necessary). Her love interest, played by John Boles (who later appeared in Frankenstein), was quite competent in his role. As most of the cast members were. In fact, all of the follow actors and actresses stood out positively as their roles: Montagu Love, Margaret Livingston, Roy D'Arcy, Burr McIntosh, Mack Swain, Bert Roach, and Carrie Daumery. Perhaps, out of all these names, the true standouts are Love, Livingston, and McIntosh.
Perhaps one of the reasons I like this film as much as I do (when I first saw it years back, I was quite happy, and luckily this rewatch hasn't changed that) is because of the large amount of suspects. True, given the film is only an hour and 17 minutes, there's not enough time to flesh out every single character and potential motivation (which, while in theory would be welcomed, it more likely than not would come out dull), but still, it's the thought that counts. The mystery was fun, more fun than many old dark house flicks (since this film takes place in a dilapidated theater house, the setting made it even more unique), and certainly still comes across as strong.
The most common print for this movie is far from perfect, with a very scratchy feel, and general lack of great preservation, but at the same time, in this case, I think it helps give the movie additional character. It does help, though, that the score is mostly solid, without any real issues.
The Last Warning is a favorite of mine from the silent era, and sadly, I think it's mostly overlooked. The Cat and the Canary and Waxworks are both far more widely-known Leni films, and how many other silent flicks are more well-known than this one? From Nosferatu to The Cabinet of Dr. Caligari, from The Phantom of the Opera to The Bat, The Last Warning has sort of been overlooked (not as badly as 1926's Midnight Faces, sure, but The Last Warning is, at least, a Leni movie), which is a great shame. Leni died in 1929 due to blood poisoning, and did fantastic things for the genre, and his final movie is no less a great addition to horror. 8.5/10 (rounded down to 9/10 to fit site's format).