[2] Lord Peter Wimsey and his friend Chief Inspector Parker hear about the death, in late 1925, of an elderly cancer sufferer named Agatha Dawson who was being cared for by her great-niece Mary Whittaker.

On the body is a £5 banknote, originally issued to a Mrs Muriel Forrest who lives in an elegant flat in London's South Audley Street.

Wimsey learns of a motive for Miss Dawson to be killed before the end of 1925: a new 'Property Act', due to come into force on 1 January 1926, that changed the law of intestacy.

Wimsey's manservant, Bunter, realises that the fingerprints on Mrs Forrest's wineglass are identical to those on a cheque written by Miss Whittaker.

She carried out the murders by injecting air into her victims' bloodstream with her hypodermic syringe, causing blockage and immediate death through heart failure.

Coming out of the prison on a sunny day with Parker, he finds a darkened world: they have emerged just at the time of the total solar eclipse.

According to James Brabazon in his biography of Sayers, she drew her ingenious and medically doubtful murder method from her familiarity with motor engines, gained from her affair with a car mechanic and motor-bike enthusiast.

That is the trouble with all the great masters – they accustom us to such dazzling performances that when they give us what would seem wonderful coming from other hands, we sniff and act choosy.

"[4] HRF Keating, writing in 1989, noted that Sayers had "invented a murder method that is appropriately dramatic and cunningly ingenious, the injection of an air-bubble with a hypodermic".

The latter, corresponding most closely with the ‘Property Act’ of the novel, swept away the old rules on intestacy[8] and specified by way of a six-point list the persons who would inherit if the intestate left neither issue nor parents.

[9] In May 1975, an adaptation was made for BBC Radio 4, produced by Simon Brett and starring Ian Carmichael as Lord Peter Wimsey.