Nurse Mabel Palmer

In the short story The Terrible Catastrophe, (later chapter 15 of The Big Four), Nurse Mabel Palmer was a nurse who came to consult Poirot about her concern that someone was poisoning her patient. She had been sent by the Lark Sisterhood to go to look after one Mr Templeton who lived at Elmstead in Herfordshire. He seemed to sudden unexplained gastric attacks with pain and vomiting. The attending physician, Dr Treves seemed to think it was normal, but Nurse Palmer had also seen the doctor together with Mrs Templeton in the garden.

Still suspicious, Palmer saved a sample of soup given to Mr Templeton which Poirot then analysed and discovered to contain quantities of antimony. This decided Poirot to go down to Elmstead immediately.

Later, Poirot discovered that Elmstead and the entire story was a trap and that quite possibly the entire household were Big Four operatives. It was not clear if Nurse Palmer was also a Big Four operative. Poirot did verify her credentials and confirmed that one Mabel Palmer was a member of the Larkhill Institute, but this may not necessarily have been the same person.