Danger Point by Patricia Wentworth

A young heiress marries impulsively and moves into her husband’s family circle, where a series of unsettling “accidents” suggests someone is trying to kill her. She turns to a discreet former governess turned private sleuth, who quietly observes the household’s jealousies, concealed relationships, and inheritance motives. By unpicking alibis and long-buried secrets, the detective exposes the ruthless culprit and prevents a final, staged mishap on the treacherous coastal cliffs.