Josephine is Sophia’s younger sister and Aristide’s granddaughter, a homely 12-year-old who is “not quite right in the head” (197). Kept away from other children at Aristide’s behest, she nonetheless has a precocious intellect that charms Charles. As the investigation into Aristide’s murder unfolds, Josephine involves herself, indulging a fascination with violence and morbidity. She hints to Charles that she knows who the murderer is but refuses to reveal a name. Charles feels protective of her and worries that her close-held knowledge might endanger her life.

Arthur and Taverner exclude Josephine from their official suspect pool because of her age until the novel’s final chapter, when Edith completes a murder-suicide to stop Josephine from doing more damage. Edith leaves behind letters revealing that Josephine indeed committed the two murders at Three Gables: “The crooked child of the little crooked house” (199) poisoned her grandfather and nanny because she was born evil due to a confluence of bad traits from both sides of her family.

Josephine encapsulates Christie’s view of evil as a fixed and immutable quality. While her wickedness was likely exacerbated by the way her parents mistreated her, she is a prototypical example of the bad seed, a born criminal with no moral compass and no chance at redemption.