This is one of the Sergeant Cribb series of detective stories set in the late nineteenth century, and in it, Sergeant Cribb is asked to investigate an investigation. Mrs Miriam Cromer has already confessed to the murder of her husband’s assistant (with cyanide, available on the premises as her husband is a photographer), and the trial is over. The hangman is on his way.
But then… doubts are raised regarding the validity of the confession. Did she really do it, or is she covering for someone else? The Home Office wants to know.
Sergeant Cribb – a far more efficient investigator than the policeman who conducted the original investigation – soon turns up some disturbing facts which cast doubt on the confession in all sorts of ways. There are inconsistencies in people’s stories, and what is the truth?
When Mr Cromer’s alibi for the time of the murder is broken and he attempts to flee to France, it seems that the confession was false, and Mrs Cromer was only trying to protect her husband (why?). But in order to extradite Mr Cromer from France, it will be necessary to pardon Mrs Cromer in order to charge him…
And that, for me, is the best part. The doctrine of Autrefois Convict (already convicted) which, together with Autrefois Acquit (already acquitted) is known as Double Jeopardy. A person cannot be retried for the same crime, on the same facts, if they have already been tried and either acquitted or convicted (unless by the request of the defence). So if Mrs Cromer is pardoned, and it subsequently comes out that Mr Cromer cannot have committed the crime because he has an alibi, what then? Even if it becomes obvious that Mrs Cromer really did do it, she can’t be tried again and will get away scot-free.
This is the plan that Mr Cromer, Mrs Cromer, and their solicitor (Mr Allingham) had hatched between them. Mrs Cromer was to confess then be pardoned in order for the police (carefully fed the facts to lead them up the garden path) to arrest Mr Cromer. Mr Allingham would then come forward with the alibi to free Mr Cromer. And even if the police knew that Mrs Cromer was really guilty, they would be able to do nothing about it.
The plan only comes to pieces when Mrs Cromer attempts to leave her husband carrying the can so that he will be hanged and she can marry Mr Allingham. Sergeant Cribb, who has uncovered the fact that the unfortunate photography assistant was not Mrs Cromer’s first murder, but her second, confronts the pair of them with this knowledge. Mr Allingham abandons the plan, refusing to go along with Mrs Cromer’s amendment, and confirming Mr Cromer’s alibi immediately, so that there is no need to pardon Mrs Cromer so that Mr Cromer can be extradited from France.
This is a very short book, and although the reader learns the facts at the same time as Sergeant Cribb, the twist at the end still comes as a surprise.