In a split second a perfect world can shatter. Only a moment ago middle-class mum, Dr. Samantha Sheppard was taking her six year old, William, to school. Now she is pacing hospital corridors, after William is hit by a speeding car. Doctors discover the child has early symptoms of a deadly disease. Only blood from a compatible donor can save him. Samantha's life is turned upside down, and she is forced to reveal her most intimate secret to her husband.