The Spider Woman is a good entry in the series and also one of the shortest with just over an hour's running time. It features a great performance from Gale Sondergaard as the villainous Adrea Spedding, whose nefarious scheme involves driving her victims to suicide with the help of an exotic venom and then collecting on their life insurance. There's good comic relief, an unnerving mute child, ingenious methods of murder, and the famous detective sports more than one disguise.

Synopsis

The film opens with a man committing suicide by defenestrating himself from a upstairs window – then we hear the cry of a newspaper seller, “Read all about your pyjama suicide”. After a few more deaths occur in similar circumstances, a concerned press and public soon start to wonder where Sherlock Holmes is, and why he isn't solving the mystery. But he's is on a restful fishing holiday in Scotland with Dr. Watson, far from the metropolis and its woes.

As they fish, Holmes tells Watson that the suicides are actually murders but despite Watson's protests, Holmes won't get involved and informs the doctor that he's finished with solving crimes, due to ill health. Holmes soon collapses and falls into the surging river below, Watson is devastated by the loss of his companion – Inspector Lestrade is not unaffected either – and after a short time, Watson decides to publish some of Holmes records. This forces Holmes to return from his faked death, disguised as a postman, and stop Watson before he discloses any sensitive information.

Holmes faked his death so he can adopt a disguise and investigate the supposed suicides; suicides that he's convinced are part of an elaborate plot by “a female Moriarty”. Holmes notes that all the victims were wealthy gamblers, so he invents the character of 'Rajni Singh', a distinguished Indian officer. Adrea Spedding's modus operandi is to seek out men short of money, persuade them to pawn their life insurance policies with her accomplices, then she kills them and collects the money. Disguised as Singh, Holmes will be her next victim.

Holmes stalks London's gaming clubs disguised as Singh, and it's not long before he meets Spedding. He looses heavily at the table and tells her he can not go on with honour in so much debt, so she offers him a solution by way of pawning his life insurance. Spedding suspects Rajni Singh is not all he appears to be, so she invites him to tea the next day where she uncovers Holmes' disguise by accidentally spilling hot tea over him, making the dye on his hand run. They both keep up the pretence however, and Holmes leaves with a sample of her fingerprints and returns to his hotel.

Lestrade is with Holmes in his hotel room, where Holmes is busy setting up the room exactly as it was for the suicides; with locked doors and sealed windows, so as to discover the method of murder. Sure enough, that night the gang strikes by introducing a deadly spider into Holmes' room via an air vent. Holmes and Lestrade give chase on the rooftops and one of the gang members falls to his death after being shot. Holmes discovers some footprints of a child near the rooftop air vent.

The world-renowned insect/arachnid expert Adam Gilflower calls at 221B Baker Street where Watson assumes that he's Holmes in another disguise, until Holmes enters the room that is. Gilflower informs Holmes that the spider is Lycosa Carnivora, “the deadliest insect known to science” whose lethal venom induces such agony that the victim is driven to suicide.

Adrea Spedding drops in on Holmes and Watson at 221B Baker St., along with Larry, a mute child. Spedding makes an attempt on their lives by the ingenious method of a chocolate bar wrapper imbued with poising, poison that spreads with the smoke after being thrown onto the fire by young Larry just prior to leaving. Luckily Holmes manages to save himself and his faithful companion.

Holmes and Watson visit the eminent ‘arachnologist’ Matthew Audway as he may have supplied the deadly creatures to Spedding's gang. Holmes soon realises that the man he is speaking to is an impostor, but the bounder manages to escape. Searching the premises, Holmes finds the corpse of the real Audway, as well as his journals which suggest something from South America immune to the spider venom. This baffles Holmes until he finds the skeleton of a pygmy, which he at first thinks is a child until Watson points out that the proportions are incorrect.

Holmes and Watson continue their search for the pygmy and the gang in a nearby sideshow at the High Holborn Arcade (look out for “Dolly Dumpling, the Fattest Lady In The World”; she wouldn't get a second look in today's rotund world), where Holmes sends Watson to fetch Lestrade. Watson and Lestrade try to blend inconspicuously into the crowd while Holmes uses a broken doll as the code to get into a fake stall but falls into the clutches of Spedding and her gang.

Bound and gagged, Holmes is tied behind a moving target in a shooting gallery, at which Lestrade and Watson obliviously take pot shots with a .22 rifle. Holmes soon manages to escape his bonds, and Lestrade and the police arrest Spedding and her gang, including the pygmy.

The film ends with Holmes theorising that the best place to commit a murder would be in a crowded place, as he and Watson melt into the throng.