Shy student Alexandra - 'X' to her friends - arrives in Naples desperate for adventure beyond the sheltered life she's led. As she explores the sun-soaked Italian city streets, she meets a man like none she has ever met before. Lord Marcus Roscarrick is handsome, charismatic and wealthy beyond all imaginings - and yet, underneath his smooth exterior, X senses he is a man well-acquainted with danger.
He begins to dazzle her in a way that she cannot resist. As they embark on a passionate affair, X is drawn further into Roscarrick's glittering world. But soon she discovers there's a darker side to him. And as he reveals his darkest secrets, and urges her to submit to his desires, X must decide: is she in too deep, or dare she take the final plunge?