After running into David outside his construction site, the two talk at a restaurant before David leaves, asking Deidre not contact him again. Deidre later has sex with a man who approaches her at the restaurant, later killing him by drowning him in the bathtub. She later watched an old sex tape of her and David before calling Lillian to torment her sexually. Deidre wormed her way into David's life by befriending Molly at the gym and (under the guise of being a child psychologist) offered to help Michael with his rage issues. Instead, while on a paddle boat together, Deidre encourages Michael's behavior and offers to teach him how to fool his therapists. When David comes home and sees Deidre with Molly and Michael, he orders her out and confronts her in the hallway, where Deidre confronts him with the fact that he tried to kill her before. He later confronted Deidre at her hotel room, where she revealed how she murdered his previous girlfriend and threatened to throw herself out the window. David stops her and orders her to stay away from his family. Deidre later used the bruises David gave her to claim to Molly that he had raped her, forcing David to confess his previous relationship with her.Deidre went on to kill one of David's neighbors to gain access to her apartment, surprising the shaky couple. While David and Molly sought out legal help, Lillian went to confront Deidre and revealed that she wanted to have her recommitted. After insulting her, Deidre feigned acceptance and went to get ready. When Lillian goes to check on her in the bathroom, Deidre smashed her head against the bathtub before drowning her in the water. Deidre then went to see David's attorney friend, whom she tells that she and David were having an affair and using their old sex tape as proof, leading the man to drop David's case. David went to Deidre's apartment to get the tape and she toys with him, stripping her clothes in the process for Molly and Michael (who were on their terrace watching). She then claimed to have sent a copy of the tape to Molly, causing David to run home to an upset Molly. When she saw the tape, she took it from Michael to play, but it instead shows a cartoon. Later that night, Deirdre went to a strip club and had a brutish man beat her up, using her injuries to claim David had assaulted and tried to kill her, causing him to be arrested.
Molly and Michael decide to go to their cottage to get away from everything while David was being released. Deidre breaks into the apartment, sees the note left by Molly, and goes to finish her off. After sneaking into the cabin, she hid until Molly was alone and attacked her with a fireplace poker, knocking her out. She then mocked Michael for crying out for his mother. When David arrived at the cabin, he found Molly tied up and gagged, and is soon joined by Deidre. David began to choke Deidre, much to her pleasure, but stops when he sees Michael watching him and decides to leave her alive so she could go back to prison where she belonged. But Deidre recovered and knocked David out before confronting Molly with the fireplace poker, calling her a "naive stupid bitch". While she is distracted, Michael took a log from the fireplace and used it to set Deidre on fire, allowing the family to escape while the cottage quickly burned down, killing Deidre.
- Yancy Butler also portrayed villainess Hannah Carmelina Santorini Frankman from Basilisk: The Serpent King, and later appeared as the evil Elena in Shark Week.
Full gallery: Deidre Kenyon (The Ex)