It's Hitchcock
As an adaptation of The Secret Agent, I found this pretty weak, but it's worth watching anyway for it's 'Hitchcockery'. A lot of elements forshadowing his works to come are present, many also reflective of his roots - the fruit stand, the suspenseful race against time, and especially the colorful supporting characters and humorous moments all smack of Hitchcock. And Sylvia Sidney gives an outstanding performance as Mrs. Verloc - although this is balanced against Oskar Homolka's performance, which seems lifted from silent film. His style is humorously over the top, all glowering and looks of utter astonishment. On the whole I'd say far from Hitch's best, but definitely worthwhile and entertaining.
"Be wary of Wenk -- I want to warn you!"