
One Dark Window
Elspeth Spindle hides a secret in a mist-locked kingdom where magic means death. Touching a forbidden Providence Card let a five-hundred-year-old spirit called Nightmare into her mind. When a highwayman attacks her uncle's carriage, she and the mysterious Ravyn Yew must gather all twelve cards before the solstice to cure their kingdom's dark magic.
What happens (ending included)
Elspeth Spindle concealed her "infection" throughout her life, since infected children who gained power from the Providence Cards were executed in the king's dungeons. After she touched one card, a five-hundred-year-old spirit called Nightmare entered her mind and often seized control of her body, gaining strength as her health failed. When a highwayman attacked her to find her uncle's Providence Cards, Nightmare aided her in defeating him. The attacker then identified himself as Ravyn Yew, the king's nephew. Elspeth and Ravyn needed to gather all twelve cards before the solstice to heal their kingdom of the dark magic afflicting it, and before the king executed Ravyn's infected younger brother and Nightmare fully consumed Elspeth's body.
Summarised from Wikipedia (CC BY-SA)

