Sherlock Holmes (Basil Rathbone) and Dr Watson (Nigel Bruce) are called to help to investigate a mysterious beast which is stalking the foggy moors. Young heir Sir Baskerville (Richard Greene) is in danger from this beast, but is the real danger from someone a bit more human...
Before the Rathbone-Bruce films entered the present day (well the 1940s), they did a couple of official Sherlock Holmes stories set in the correct period, of which this was the first. Their characters arn't quite set yet but they do a very good job with a classic story.
Its a very atmospheric story though the foggy (and presumably chilly) moors reverberate with the sound of crickets for some reason.