Treason's Daughter by Antonia Senior
Love, betrayal and a family divided amid the turmoil of the English Civil War.
London, 1640. Fifteen-year-old Henrietta Challoner dreams of adventure, of a life lived at the gallop, of the opportunities afforded to her brothers, Ned and Sam. She cannot know how devastatingly real these dreams will become, as the country slides towards vicious civil war...
The crisis threatens to tear Henrietta's family apart. As religious and political tensions spill into the streets, they all must decide what comes first - their family, their country or their desires. But while she strives to maintain the peace at home, Henrietta becomes embroiled in a deeper plot: to hand London over to the King.