Twelve-year-old Annette Nolan lies in a hospital bed in St Mary's in Dublin. She has acute leukaemia. Dr. John Nicholson tried to explain everything to her in simple terms.
Events leading up to this include Nicholson's efforts to find a suitable drug therapy for cancer; these were described in A Matter of Conscience. His work continues in Professor Walter Wainwright’s Department of Oncology in Trinity College Dublin and St. Mary's Hospital. Progress is made until the sudden death of Professor Wainwright. This leaves the Chair of Oncology vacant. Nicholson applies for the position but fails. Working conditions become difficult and frustration sets in.
An invitation from Sir Kenneth Richardson is received by Nicholson to join the research team in the Newton Foundation in Cambridge University. He accepts a senior position and a consultant post in Addenbrooke's Hospital.
Nicholson's research makes a spectacular breakthrough using a new method not involving animals. Matters are made worse when he speaks out against animal research at an Oxford Union debate. An attempt is made on his life. The police are called in and the mystery deepens.
In spite of this he continues his original work and encounters many pitfalls including self-seeking and jealous colleagues, implacable bureaucracy and uncovers answers to important and uncomfortable questions.
Events build up to a haunting conclusion when he makes the greatest sacrifice anyone can make to save a young person's life.