The figure of the mistress is undoubtedly controversial. She provokes intense reactions, ranging from fear, to disgust and revulsion, to excitement and titillation, to sadness and perhaps to some, love. The mistress is conventionally depicted as a threat to moral living and someone whose sexuality is considered defective and toxic. Of course, she is a woman that you would not have as your friend, and certainly not your wife, since her ethical sense, if she even has one, is dubious at best. This book subverts these traditional judgements and offers an unflinching look at the lived experience of the mistress. Here she is recast as a potentially loving, free, intimate 'other' woman. Drawing upon feminist philosophy, contemporary sexual ethics and the current cultural moment of #MeToo, moves beyond a narrative of infidelity, conventional judgment, the safeguarding of monogamy and conventional heterosex that permeates our society. It asks what happens when we let go of our insecurities, judgments and moralistic relationship philosophies and opt, instead, for an ethics of kindness. This kindness – underpinned by engaging with those deemed 'other' and learning from mistresses, both straight and queer – will teach us new ways of thinking about ethics and sex, and reveal how we have better sex, and how we can be better to each other.