The talk of London is the spate of sensational suicides dubbed the "Pyjama Suicides" due to the dead being found in their night clothes. Where is Sherlock Holmes (Basil Rathbone) when the city needs him to solve the mystery of these tragedies? He's enjoying a fishing holiday up in Scotland with his constant companion Dr John Watson (Nigel Bruce), and while he stands by the river's edge, Watson reads about the deaths in the newspaper, wondering why his friend hasn't done anything about them. When he confronts Holmes, the great detective tells him that they are no suicides but really murders, but he won't do anything to stop them as he has been feeling dangerously ill recently...
Cobbled together from bits and pieces of Arthur Conan Doyle stories by Bertram Millhauser, The Spider Woman (its onscreen title) emerges as one of the better efforts in this series. It begins with Holmes suffering a dizzy spell and taking a tumble into the waters, leaving everyone assuming he's dead - how little they know him. Even Watson is in mourning, and makes plans to send Holmes' effects and scrapbooks to the British Museum with the help of Inspector Lestrade (Dennis Hoey). This is a particularly eventful instalment, and no viewer will be taken aback when the postman who turns up to deliver a letter to Watson turns out to be a certain someone in disguise.
Rathbone has a lot of fun with his disguises, and of course the gullible Watson has trouble seeing through them, but is immensely relieved when the trick is revealed ("Holmes!", he vociferates, practically collapsing to comic effect). Sherlock has decided that the mastermind behind the "suicides" is female, as we may have guessed from the title, even though it's difficult to guess why he had to fake his own death to instigate the investigation. Nevertheless, he dons yet another disguise, this time an Indian nobleman with a paralysed arm, to go undercover and lure the woman, who we now know to be one Adrea Spedding (Gale Sondergaard), into a trap.
One of the strongest elements of this film is that the villainess is more than a match for the heroes - until the finale, anyway. Sondergaard is a female Moriarty, with an apparent network of henchmen who do her bidding, and to see her pit her wits against Holmes in slyly amusing scenes makes for winning entertainment. See the sequence where Holmes in his Indian disguise goes round to Miss Spedding's for a cup of tea, thinking he has the upper hand at first, but realising that she is onto him when she "accidentally" splashes hot tea onto him, wiping away some of his dusky makeup. With both sides aware of each other's motives, the suspense is better than the more average entries.
Another thing that makes this stand out is that the bumbling Watson is actually some use to working out the plot for a change. Sure, he plays the tuba for no good reason, and mistakes a bearded entomologist for Holmes, but he also puts the detective on the right track as to how Spedding commits the murders. With large, poisonous spiders and an apparent killer child, there's a welcome touch of the macabre to The Spider Woman, and the pace moves along like a contemporary serial from one death defying exploit to another, including an ingenious way of knocking out Holmes and Watson in their own flat on the part of the baddie. The film sees both Rathbone and Bruce at their most typical and endearing, and is justifiably regarded as one of the gems in this set of adaptations. Sondergaard returned in The Spider Woman Strikes Back.