When several wealthy gamblers are found dead in their beds with no visible sign of forced entry or foul play, it's a case made for the Baker Street sleuth. Sherlock Holmes (Basil Rathbone) and ever-trusty assistant Dr. Watson (Nigel Bruce) investigate these "pajama suicides," and when Holmes meets the alluring but cryptic Adria (Gale Sondergaard), he suspects this so-called "Spider Woman" of being the mastermind behind the murders.