My husband’s mistress rang my doorbell, handed me her coat, and said, ‘Tell Richard I’m here.’ She thought I was the help. In my own house. She didn’t know I was his wife of 12 years — or that I owned the company her father worked for. Twenty minutes later, Richard walked in. By nightfall, he was packing a suitcase. And three weeks later, I made a call that would cost him everything…