In the novel Evil Under the Sun, Nellie Parsons was a young servant girl who was was found murdered some time before the events on Smugglers' Island. Her body had was found in Marley Copse near Chobham in Surrey. The newspapers called it “the Lonely Copse Mystery”.
Later another woman, Alice Corrigan, was found murdered just ten miles away. At first the police did not link the two cases because there was a natural suspect for Alice's murder in the person of her husband. When he produced a solid alibi, the police began to link the two cases especially because both had been killed by the same method: strangulation. They believed that both had been killed by the same person but no one was ever caught. Hercule Poirot couldn’t say for sure if Nellie was murdered by Patrick Redfern or not.