Winking at the Brim — Gladys Mitchell

As Laura goes through the mail in "Winking At The Brim", she finds a letter addressed to Sally Lastrange, Dame Beatrice's young niece who is visiting and who is looking for more permanent living conditions. The letter is an invitation for Sally to attend the birthday party of her schoolmate Phyllis Calshott. Even though she has a low opinion of Sally, she feels that she has to go.