Kerstin Kvist didn’t quite know what to expect when she took up a job with the Cosway family at their odd, almost grand home, Lydstep Old Hall, deep in the Essex countryside.

The family turned out to be even odder than the house: the widowed Mrs Cosway lived with her three unmarried daughters, in thrall to the old lady. A mysterious fourth daughter - a widow herself and apparently quite rich - came and went, with ill-disguised contempt for the others. More puzzling still was Mrs Cosway’s son, John, a sad, self-absorbed figure in his 30s who haunted the house.

There’s ‘madness in the family’ offered one of the daughters by way of explanation, but Kerstin had trained as a nurse and knew it wasn’t right to be administering such powerful drugs to a vulnerable figure like John …