This article contains plot spoilers for the 2017 series of Twin Peaks.
Phyllis Hastings was the wife of William Hastings.
While in the zone with Ruth Davenport, William was attacked by several people who grabbed him around the neck and demanded to know Phyllis' name. Subsequently, Phyllis had an arrangement with Dale Cooper's doppelganger.
After Bill could not be released on bail, she was allowed to briefly see her husband in his jail cell. He insisted that he was never in Ruth's apartment, but he had had a nightmare that night. She then accused him of having an affair with Ruth, which was followed by him stating his awareness of her affair with George, and possibly someone else as well. She taunted him with "life in prison," and was dismissed. She informed George that Bill was made aware of the affair, but requested him not to leave with her, though they did plan on meeting at her house later on.