Brilliant heart surgeon Charlotte Roberts and her husband, consultant anaesthetist Jacob are a high-flying busy married couple. But things soon turn upside down when their mysterious new hospital colleague Mia rents out the house next door. Working her way into Charlotte and Jacob's confidence and eventually their bed, Mia also quickly befriends cul-de-sac outcast Alan whilst Charlotte has to handle the reappearance of past flame Leo.

However, it's not long before Mia's past comes back to haunt her, leading Charlotte and Jacob to question who she really is, especially when patients at the hospital mysteriously start dying. But one thing is clear, giving into desires can have deadly consequences…