The arrival of “Holmes” (Basil Rathbone) and “Watson” (Nigel Bruce) in Canada for a seminar led by “Lord Penrose” (Paul Cavanagh), a regular in the series, highlights a difference in their methods – his reliance on science versus Lord Penrose's more intuitive approach. However, that’s not the main concern when they are compelled to go to the gloomy village of “La Mort Rouge” to look into the violent death of “Lady Penrose.” The murder is wrapped up in an enigma reminiscent of "The Hound of the Baskervilles," but predictably, “Holmes” dismisses any notions of supernatural creatures – particularly as people continue to die, the doctor keeps getting trapped in muddy areas and this small community seems to have many possible suspects. Nigel Bruce has a more significant role in this installment, which I appreciated, and there's a good amount of story to engage with. This time around, even the viewers are kept guessing, and there’s a generous supply of misleading clues within this unsettling setting filled with disguises, noisy floorboards, and an enormous dog designed to hold our attention. I would say that this is my favorite entry in the series; it's genuinely frightening when you watch it on a dark evening while listening to rain against the window.

Source on TMDB