The mother-in-law / Sally Hepworth.

Someone once told me that you have two families in your life - the one you are born into and the one you choose. Yes, you may get to choose your partner, but you don't choose your mother-in-law. The cackling mercenaries of fate determine it all. From the moment Lucy met Diana, she was kept at arm's length. Diana is exquisitely polite, but Lucy knows, even after marrying Oliver, that they'll never have the closeness she'd been hoping for. But who could fault Diana? She was a pillar of the community, an advocate for social justice, the matriarch of a loving family. Lucy had wanted so much to please her new mother-in-law. That was ten years ago. Now, Diana has been found dead, leaving a suicide note. But the autopsy reveals evidence of suffocation. And everyone in the family is hiding something...