This Was a Woman plot
Sylvia Russell is a very matriarchal woman, to the point of morbidity. She has a lot of influence on her daughter Fenella and her son Terry and completely determines their actions. Silvia manages to ruin her daughter's marriage by having her waitress seduce her brother-in-law, and similarly she destroys her son's marriage by forcing the same waitress to seduce her son. One day, Silvia Valentine meets Christie, a young friend of her husband Arthur, whom she wants to possess. She therefore seeks an opportunity to poison her wimpy husband.