Anstey is crossing Hampstead Heath one night when, just after a man runs past him, he hears a woman crying for help in the other direction. He finds her in time to see her knocked down and her attacker get away.
The mysterious woman has been stabbed and Anstey carries her to a nearby house to seek aid. Just as he arrives, he hears the terrified housekeeper Mrs Benham calling the police, for her master Andrew Drayton has been murdered in his small private museum of inscribed objects -- lace bobbins, ornaments, jewelry, and the like.
The dead man is the brother of Sir Lawrence Drayton, a neighbour of Anstey's in the Temple as well as an acquaintance of Dr Thorndyke's, who is brought in to investigate while the police pursue their own enquiries. Anstey has acted as Thorndyke's leading counsel for years and, in order to provide him with useful evidence, takes -- illegally, one would think -- two pieces of fingerprinted broken glass away from the crime scene.
The injured woman, Winifred Blake is interested in inscribed jewels and had visited Drayton that evening to look at his collection. She had hardly entered the house when he was shot in another room, and in foolishly trying to follow a man escaping from the scene was herself assaulted. Evidence shows two criminals were involved and that certain items of jewelry have been stolen.
The plot then thickens into a rich stew whose ingredients include Biblical verses with no apparent relation to each other, a good luck charm made from a porcupine ant-eater bone, a strand of blue hair, spectacles which allow the wearer to see what is happening behind him, and a mystery within a mystery.
My verdict: A particularly rich plot featuring a dash of romance, with clues realised to be in plain sight once the reader knows the solution. The novel includes some interesting asides, such as an explanation of how Scotland Yard's Habitual Criminals Registry compares hundreds of fingerprint records kept on cards when seeking matches to a particular set of dabs. The preface mentions a particular incident, identical to one that happened in real life, was already in a chapter written some time before the actual event occurred.