Using rules and axioms, there will always be some propositions that can't be proved either true or false. But can this apply to murder? Godel's Theorem of Incompleteness is familiar territory to the young South American mathematician who arrives in Oxford. Murder, however, is not. Yet barely has he greeted his elderly landlady - and her rather luscious granddaughter - when he is bidding her a posthumous farewell. Mrs Eagleton is murdered in her wheelchair. The only clue to the crime is a cryptic symbol and the words 'the first in the series'. It's not much to go on, but it's enough to appeal to Arthur Seldom, one of the leading minds in logic. His most famous work of philosophy contains a chapter on serial killers. This killer, clearly, has read it. And the second murder, of an elderly hospital patient, confirms that his methods of killing are deliberately designed to appeal to mathematicians. And that he's an intellectual megalomaniac...