For a film called Blackmail, the blackmail element is rather minimal and introduced very late in the story. Most of the movie is of the events leading up to it. But it's adapted from a play of the same name, so I suppose there’s nothing for it.
This is Britain's first talkie, sort of. It started as a silent feature but certain scenes were reshot with audio for theaters wired for such. Pretty Anny Ondra, the first Hitchcock Blonde, had a thick Czech accent so she was dubbed, Lina Lamont style. I sadly recorded the silent version.
The Hitchcock style really starts to show through here, more so than even The Lodger. And the plot is quite good: A man investigates the murder of a man that his girlfriend (perhaps fiancee) is suspected of killing.
Blackmail is pretty good but Hitchcock would do his best work fully in the sound era. I would have liked to have seen the “talkie” version, but I don’t expect it would have been much better. AMRU 3.5.