If an employee, as part of a programme of industrial action, refuses to work normally, what is the legal position when he performs only a part of his duties? This question has been the subject of much litigation in recent years, and raises issues of fundamental importance. At a practical level, it has to be determined whether and when the employee is entitled to any remuneration, and if so, how much? Related to this are the options open to the employer in the light of such action. At a theoretical level, questions arise concerning the proper scope of the law of contract, and its relationship to the law of restitution. This paper will explore these issues, and suggest an approach which can adequately deal with both questions.