Governess to the Duke’s Heir by Maggi Andersen

Andrew, the Duke of Harrow, has returned to his Oxfordshire estate after years away in Vienna on a diplomatic engagement. He left England after losing his beloved wife in childbirth. But his children consider him a stranger, and the new governess disapproves of him.
In hope of restoring his family, he has invited a German baroness who may become the new Duchess of Harrow, and her brother, as his guests. Andrew’s plans do not go to order. Were there three attempts made on his young son William’s life, or are they a string of amazing coincidences? Why would anyone want to harm William? Andrew finds himself working with the governess to discover the truth while keeping his son safe, and disconcertingly, comes to depend on Miss Harrismith, as his respect for her deepens. When the truth finally becomes clear, Andrew faces his feelings, but then finds his chance of happiness snatched away.
Miss Jenny Harrismith, the daughter of an impoverished baron from Yorkshire with six children, leaves home after a disagreement with her father, taking a position as governess to the Duke of Harrow’s two children. After a year at Castlebridge, when the duke barely makes an appearance, she has found a certain peace, and become very fond of her charges. But the duke has arrived home to stay, and suddenly, there is no peace to be found. Frightening things begin to happen. As she fights to keep the duke’s son safe, she finds herself falling in love with his father.
Thrust into danger, and coming close to death, she realizes she must face the truth of what she left behind in York.