µ is a female cat who once belonged to the mathematicians Archimedes and Pythagoras Vavasor. Following their deaths, she was looked after by their erstwhile housekeeper Mrs Standage. She is black with white socks and is of mixed heritage. Despite her small size, she is feisty and assertive and does not recognise any superior authority. Given her former position in the Vavasor household, she is probably privy to more secrets than any human alive. She has, however, not yet seen fit to share them with anyone else.