Late one night, Dr. John Strangeways is summoned to tend to a woman who has clearly been strangled. Deeply unsettled by the odd encounter, he has cause to remember one of the men who was at that scene when chance brings them together in Rochester a year later. The man in question, in possession of a wicked-looking knife, does not remember the doctor, however, and Strangeways, new in town and on his way to look over a recently-vacated surgery, is relieved to be unable to help when the man asks for directions to the residence of Mrs. Frood. Deciding to take the practice on, Strangeways is in due course introduced to his landlady, and comes face to face with the strangled woman of a year before. Her name? Mrs. Angelina Frood.