 Mrs. Alice Pengelley arrives in London to visit Poirot, telling him she is being poisoned by her husband. She is convinced her husband is putting weed killer into her food. Poirot makes a trip the next day to visit her in Cornwall, only to find he is too late - Mrs. Pengelley is dead. The main suspect is Mr. Pengelley, her husband, who is having an affair with his young medical assistant. However, Mrs. Pengelley s niece may also be a suspect, as she is in her aunt s will for 2000 pounds. The niece s fiancé may also be involved, as he has apparently been flirting with Mrs. Pengelley while also courting her niece. And what of Mrs. Pengelley s doctor, who changes his story about her condition once he is on the stand testifying against Mr. Pengelley. And the maid seems out to get Mr. Pengelley as well. It all comes to a head when Poirot corners the killer and obtains a written confession, promising the murderer 24 hours head start to get out of town before giving the confession to the police - a promise Poirot does not keep.