This is book four of the Adam Dalgliesh series. It was written in 1971. Phyllis Dorothy James continued to write until her death in 2014 at the age of 94.
This story involves the deaths of two third-year nursing students. Dalgliesh, a chief superintendent no less, is sent to investigate at the request of the local chief inspector. Both deaths were caused by poisons and Dalgliesh had no trouble identifying suspects, but did have trouble discovering motives.
James, like many women authors, gives us a good look at each main character and his or her inner emotions. Unlike some, she does not overdo it. She maintains good pace and tension, making this book a good read.