Sir Wilfrid Robarts, a master barrister in ill health, takes on Leonard Vole as a client, despite the objections of his private nurse, Miss Plimsoll, who says the doctor warns him against taking on any criminal cases. Leonard is accused of murdering Mrs. Emily French, a rich, older widow who had become enamoured of him, going so far as to make him the main beneficiary of her will. Strong circumstantial evidence points to Leonard as the killer, but Sir Wilfrid believes Vole is innocent.