The "hopping boy" with cat-quick reflexes is one of the most unusual and unsettling figures of the decade. I don't think I've ever seen such an imaginative and offbeat use of a young person in any other movie. The film itself has many imaginative touches, but among them, it's that bizarre little "hop" (never explained, and neither is the boy) that's so memorable. He's a perfect adjunct to the leeringly evil Adrea (Sondergaard) who looks like she's having a delicious time playing cat-and-mouse with the tricky Sherlock (Rathbone). In fact, their devious encounters are models of beautifully "layered" acting as each has several things going on internally at the same time. She's a perfect foil for the master detective, with a flashy smile that says one thing while her eyes say another. Too bad the imperious Sondergaard was lost to the blacklist of the early 50's.
I never did figure out just how the pygmy (Angelo Rossito in blackface) fit into the suicide scheme, but that's okay because the movie has so many intriguing touches, including the highly contrived but suspenseful climax. Even Hoey's Inspector Lestrade is wisely restrained, and when he walks off proudly arm-in-arm with the eye-catching Adrea at the end, it's a rather charming little moment. I guess my only complaint is with the poorly done process shot of the raging river that contrasts starkly with the well-stocked foreground. Nonetheless, this is one of the most imaginative entries of any detective series of the period.