American-born British MP and former prison warden. Motivated by fear of exposure, she murders Emily Boynton and a young witness to protect her reputation. Commits suicide after Poirot reveals her guilt, avoiding prison. Poirot ultimately classifies her death as an accident to preserve her legacy.
Emily recognizes Westholme's hidden past and uses it to threaten her.
The protagonist detective uncovers and confronts the true killer.
Westholme and Quinton travel together as part of the same expedition group.
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