Cynthia Slayton

Cynthia Slayton is the main villainess from "The Best Seller," episode 4.04 of Matlock.

She was played by Tricia O'Neil.

Cynthia Slayton is a famous romance novelist and the wife of Phillip Slayton, who is also her business manager. She was shown being interviewed regarding her success, though when it was over, Cynthia's true personality was revealed, as she was a very irritable and unlikable woman. As for her novels, Cynthia had been stuck on ideas for a while, until she decided to write one about a woman who finds out that her husband was having an affair with her best friend, so she plans a murderous revenge. She later stopped writing due to the fact that she believed that life was imitating art:  she had suspected that Phillip was cheating on her with her best friend and assistant, Elizabeth Lyle. Just as her novel's protagonist did, Cynthia became a villainess hellbent on revenge.

Cynthia's plan began with poisoning her own allergy medication, getting a prescription of the poison and then contaminating every pill in her bottle, which was picked up by Phillip. Knowing that Elizabeth was allergic to cats, the evil Cynthia placed her cat inside the house to trigger a sneezing fit from Elizabeth, leading to Cynthia giving her the bottle of poisoned medication. Elizabeth took one of the pills and later dropped dead, and because Phillip picked up the medication, he was accused of attempting to kill Cynthia (though it was never uncovered if framing Phillip was part of Cynthia's plan).

Phillip did confess to having an affair later in the episode, making his confession to Cynthia at the episode's midpoint after having enough of his wife's antagonistic behavior. Cynthia dismissed the confession believing that it was about Phillip's past affair, but was shocked to learn that not only was it about an ongoing affair, but that the other woman was Cynthia's sister, Joanna Morrell. Cynthia threw both of them out, and later on, Julie March and Tyler Hudson uncovered Cynthia's saved novel, which ended up giving her away as the murderess. Ben Matlock's cross-examination of Cynthia uncovered her villainous plan, with Cynthia denying everything until Matlock uncovered evidence of her actions. Matlock later reminded Cynthia that she had killed the wrong person, as Phillip's affair was with Joanna. After the reveal, Cynthia was arrested (off-screen) for killing Elizabeth.