Having watched the trial of Harriet Vane, an authoress accused of murdering her former lover, Wimsey has become convinced that the woman is innocent, and is thrilled when the murder trial results in a hung jury, requiring another trial a month later. Wimsey decides to prove Harriet’s innocence and interviews her, proposing marriage as he does so. Harriet rightly thanks him for his assistance, and even more rightly rejects him. Wimsey isn’t deterred from either goal.
Being locked up in jail the whole time, Harriet isn’t given a lot to do in her first appearance besides stand by her beliefs (strange at a glance, but understandable when you think about them) and say “Well, you seem like a perfectly nice and likable man, and I’m very happy you’re trying to save my life, but I barely know you, so would you mind not proposing to me in jail every time we meet? It’s a bit uncomfortable. Especially given that my last relationship was a man testing my worthiness as his wife.”