Lorac, the pen name of the British writer Edith Caroline Rivett.

[1][2] It is the fourth book featuring Chief Inspector MacDonald of Scotland Yard who appeared in a lengthy series of novels during the Golden Age of Detective Fiction.

[3] Colonel Marchand is found dead, apparently from cyanide poisoning, after hosting an attractive young woman for tea.

There are numerous potential suspects including his various servants, secretary and his spendthrift heir.

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