If there is anyone who has been in St. Mary Mead longer than the town gossips, it's Dr. Haydock. He is an elderly gentleman who is Miss Marple's physician as well as the police surgeon; he lives next door to the Vicarage. He saw to it always that Miss Marple was healthy while she went about her detective duties, and he even enjoyed talking to Miss Marple about cases. He believes that criminal behavior results in physical malfunction.
He was at the scene of the crime shortly after Protheroe's death and gave evidence of the time of death and cleared Lawrence Redding from suspicion. To help Marple along in her health, Haydock even tells her a story about the death of Louise Laxton, a young woman in the village; Jane Marple, of course, helps Haydock out by giving the solution. By the time Gossington Hall was sold to the famous actress Marina Gregg, Haydock was "semi-retired" and had an assistant named Dr. Sandford.