Amy, a compassionate nurse and single mother struggling with a life-threatening heart condition, is stretched to her physical and emotional limits by the hard and demanding night shifts at the ICU. But help arrives when Charlie, a thoughtful and empathetic fellow nurse, starts at her unit. While sharing long nights at the hospital, the two develop a strong and devoted friendship, and for the first time in years, Amy truly has faith in her and her young daughters' future. But after a series of mysterious patient deaths sets off an investigation that points to Charlie as the prime suspect, Amy is forced to risk her life and the safety of her children to uncover the truth.