Harriet Vane, a crime writer, is charged with poisoning Philip Boyes, her former lover, with arsenic. The evidence against her seems overwhelming, but it is all circumstantial. The jury is divided and a new trial is ordered, to begin in four weeks' time. Wimsey visits Harriet, finds himself falling in love with her, and sets out to clear her name.

Lord Peter asks Miss Murchison to go undercover has a secretary at Norman Urquhart's law firm. She learns he was illegitimate and now paying for a nurse to care for his mother. Insp. Parker confirms Philip Boyes was definitely poisoned.

Lord Peter asks his secretary Miss Climpson to find out what Urquhart's nurse Miss Booth knows. Faking a seance Miss Booth admits that Urquhart has forged Philip Boyes Will to make him the sole beneficiary but can Lord Peter break him.