Inspector French: Sudden Death

To mark the publishing centenary of Freeman Wills Crofts, 'The King of Detective Story Writers', this is one of six classic crime novels being issued in 2020 featuring Inspector French, coming soon to television. Anne Day is the new housekeeper at Frayle, the home of Mr Grinsmead and his invalid wife. To Anne's horror, her intuition that something is very wrong in the house culminates in an unexpected death.
With the police jumping to devastating conclusions, Inspector French arrives to investigate. With the narrative switching between Anne's and French's perspectives, giving alternately the outside and inside track of an ingenious and elaborate investigation, will tragedy strike a second time before the mystery is solved?