The Killian Series

Abigail Garen isn't your typical nanny. Her superiors, a mysterious group known as The Council, send her to a private island off the coast of Scotland on a mission: save Elspeth Killian, a ten-year-old girl that's never left the sixteenth-century castle she calls home...and the daughter of one of the world's most powerful criminals.
Dubhaile Killian is a genius when it comes to weaponry and robotic technology. But when it comes to showing his love for his only daughter, he's far from being father of the year.
Dangerously paranoid, he's convinced that Abigail is a spy, sent by an organization that's been closely monitoring him for years. But The Council isn't an intelligence agency-they, like Abigail, aren't even human-and his suspicions about their motives couldn't be further from the truth.
As Abigail attempts to manipulate Elspeth and survive Dubhaile's constant tests and interrogations, she sees something in the drug-addicted, violent, and unstable monster that is Mr. Killian, experiencing an unexpected change of heart. But when The Council sends someone else to finish the job for her, Abigail is forced to protect her newfound family, and ask where to draw the line between orders and matters of the heart.