Hazel Hughes has spent her life believing she is a Medium - someone who can talk to ghosts. But as of yet, that skill has remained frustratingly elusive. She is also suffering from a reoccurring childhood dream of someone who looks almost exactly like Hazel, but this dream version of herself is slowly going mad.

Sam MacInnes is a talented surgeon who runs in the highest social circles thanks to his family's position and history. When Sam hires Hazel to assist him with his medical practice, he is immediately drawn to her intelligence, wit, and beauty. Their potential relationship is derailed one evening when a mysterious count arrives in London and reveals to Hazel the truth about her past: she was abducted at birth and her twin sister has fallen dangerously ill.

Hazel agrees to travel to Romania with Count Petrescu in order to save her sister, and Sam insists on accompanying her. The count has secrets, though, and the journey grows more sinister with every mile that draws Hazel closer to her homeland. Even as her feelings for Sam become deeper and more complicated, she fears she might not survive the quest to save her sister with her heart intact, not to mention her life. She must learn to draw on gifts she doesn't know she has if they are going to ever return home again.

Hazel and Sam must fight their way past dark magic, clockwork beasts, and their own insecurities as they try to reach her sister in the impenetrable Coppergate Tower before time runs out.