Final answer:
Based on the information provided, it can be inferred that Mrs. Stevenson might be the intended victim of the murder plot.
Step-by-step explanation:
Based on the details provided by the author about the setting and the murder plot, it can be inferred that Mrs. Stevenson herself might be the intended victim. The author mentions that Mrs. Stevenson overhears the murder plot, indicating that she is in close proximity to the intended victim. Additionally, the author provides details about Mrs. Stevenson's fears and anxieties, suggesting that she is in danger and may be the target of the planned murder.