Near the end of Chapter 10, Mary Cavendish, Hercule Poirot, and Captain Arthur Hastings walk together from the village back to Styles Court. As they go, Hastings (as the narrator) observes the ominous weather:
The weather had broken, and the sharp wind was almost autumnal in its shrewishness. Mary shivered a little, and buttoned her black sports coat closer. The wind through the trees made a mournful noise, like some giant sighing.
Hastings’s observations about the weather are very telling. Personifying the “sharp” wind as both "shrewish" and "mournful," he invokes a cold sense of heavy, ongoing, and imminent grief. This feeling is only emphasized by the fact that he characterizes the wind as though it is "sighing" with some secret trouble. This personification of the weather mirrors the feelings of the characters walking back to Styles Court—especially Mary, who seems to have some unspeakable secret that she is hiding and may need to confess. Hastings’s own feelings for Mary color the exchange, as he witnesses her discomfort and isolation, and the toll that her unknown secret takes on her. Poirot's disappointment in Mary's lack of forthcomingness is also reflected by this description of the wind, as his desire to solve the case is impeded by his inability to gather information.