Lady Sally Edensor is the mother of Will Edensor, and the wife of Sir Colin Edensor.  The book starts with a series of letters between Sir Colin and Lady Edensor and their son Will.  Will’s parents are pleading with him to meet them. It’s clear from the letters that Colin and Sally are extremely worried about Will. The letters take on a more desperate tone as we learn that Sally has been diagnosed with a serious illness.

We learn from a letter from December 2015 that Sally has been given three months to live, and then hear that she died on 1st January 2016 having still not seen Will, despite telling him that it was her dying wish.

When Strike and Robin meet with Sir Colin Edensor and his two older sons to discuss the Agency taking their case, Ed Edensor explains that Will did not attend the funeral of his mother.  Sir Colin says his wife’s last conscious act was to beg Sir Colin to get Will out of the UHC (Ch 4).