This chapter explores the moral aspect of provocation, namely the defendant's claim that their violence was in some way understandable in the circumstances. It discusses the moral compromise involved in the provocation defence, the possible relevance of ancient attitudes towards revenge and the awkward relationship between law and retaliatory killing. In Euripides' Electra, the young avengers Orestes and his sister Electra repeatedly speak in terms of the duty to repay a debt and the rhetoric of the chorus and other characters echo this. Unlike Hamlet, Electra herself does not agonize about carrying out the revenge. In modern law, the English and US approaches to the moral aspect of the provocation defence are as different as they are in their approaches to the psychological aspect. The chapter considers the moral content of the modern provocation defence, namely the standard of the 'reasonable man' in English law, and the limited set of legally recognized provocations in US laws of homicide.