An arms dealer with a heart problem is too ill to stand trial and taken to a teaching hospital for treatment. Dalgliesh questions him and tensions among the nurses and other medical staff start to be revealed.

Despite being present during the death of one of the student nurses, Dalgliesh is not asked run the investigation. Further relationships between the staff are revealed. Dettinger, the arms dealer, recognizes somebody from his past.

Following the death of a second student nurse, and that of the arms dealer Dettinger, Dalgliesh is put in charge of investigating all three deaths due to the potential links between the cases. Potential motives start to be revealed.

Dalgliesh starts to make progress despite the lies and evasions of the people who have been interviewed. Dettinger's final words, as told to his wife, reveal a dark past for one of the nurses.

As the story reaches its climax, history catches up with the older staff. A blaze due to arson at the summer house reveals yet another body. Dalgliesh solves the murders of the nurses but struggles to find enough evidence to prevent further loss of life.