Miss Blacklock’s pearl choker symbolizes deception and concealment. The large “false-looking” pearls appear “incongruous” as they do not fit with Miss Blacklock’s understated appearance and manner—a clue to her lack of authenticity. At several points in the case, Inspector Craddock wonders if the pearls may be genuine and, therefore, highly valuable. However, the choker’s significance lies not in what it is worth but in what it conceals. The necklace is a disguise, covering the surgical scar that identifies Miss Blacklock as Charlotte.

While the choker represents Miss Blacklock’s duplicity, that duplicity relates to her identity and, consequently, her innermost world; the choker thus also acts as a barometer of her state of mind. When her character is first introduced, the choker represents her impressive veneer of composure. As that veneer begins to crack, she touches the choker when agitated as if to check that her disguise is still in place. The moment when the choker breaks signals that the character herself is “breaking” as she feels forced into increasingly extreme measures to protect her identity.

The motif of sight is introduced with the blackout at Little Paddocks. Miss Blacklock engineers the lights’ shorting to ensure no one witnesses the murder, and the outage highlights the unreliability of sight.