Mysterious intruders infiltrating the mind of every individual on the planet in order to monitor for potential threats to a civilisation beyond mankind's reach is the stuff of science fiction movies, isn't it? For BBC researcher Andy Crawford, however, a reoccurrence of disturbing dreams confirms unequivocally that unwarranted intrusions from an enigmatic entity are only too real. Inevitably, communication is firmly established between both parties and our protagonist is profoundly shocked to learn of the monumental task he has been instructed to fulfil. His initial reaction is to reject it out of hand, but he eventually finds himself confronted by an impossible dilemma which requires a great deal of rational thought. With his marriage crumbling around him and his professional life in jeopardy, the question is whether or not his personal problems will affect his decision making. Even though it is morally wrong, will he ultimately be persuaded to complete the assignment that he has been given?