Ainsley is a bank branch manager and mother of three who views herself as a problem solver. Feeling her marriage deteriorate after years of prioritizing work and childcare, she proposes an unconventional solution to save it: scheduling one night a week for each of them to date someone else. She creates a profile on the Dater app under the pseudonym 'Annie Green' to organize her encounters. She maintains a calm, structured exterior while attempting to manage the emotional fallout of her plan.

Peter is an architect who has grown emotionally distant from his wife and family. He reluctantly agrees to Ainsley's open-marriage proposal out of fear of losing her, adopting the pseudonym 'Pete Patterson' on the dating app. He struggles with intense jealousy and the psychological weight of their new arrangement, especially when his actions begin affecting his professional life at the firm.

Stefan is a widower and active police officer in his mid-forties. He matches with Ainsley on the Dater app and meets her for her first scheduled arrangement night. He quickly becomes emotionally invested and persistent, pushing well past the boundaries of the casual encounter Ainsley originally proposed.

Illiana is a determined and observant woman who launches a personal inquiry into Ainsley's life. Her search for the truth brings her directly into the Greenburgs' orbit. She refuses to accept easy explanations and actively tracks down those she believes have wronged her family.

Glennon is Ainsley's loyal best friend who runs a nonprofit organization. She frequently drops by the Greenburg home and is highly observant of the tension between Ainsley and Peter. She acts as a confidante for Ainsley while managing her own complicated marriage to Seth.

Seth is Glennon's husband. He works in business and presents a polished, successful exterior during social gatherings with the Greenburgs. He is friendly with Peter and frequently hosts events at his home to maintain his family's social standing.

Gina is an attractive partner at the architectural firm where Peter works. She discovers Peter's profile on the dating app and directly expresses interest in him. She pursues a casual connection, bringing awkward complications directly into Peter's workplace.

Mallory is a massage therapist in her mid-twenties. She matches with Peter on the dating app and immediately pursues a physical relationship with him. She brings an uninhibited, chaotic energy into his new open-marriage arrangement.

Dylan is Ainsley and Peter's 14-year-old son. He notices the shifting dynamics in his home and occasionally questions his parents' strange behavior. His physical presence in the house forces Ainsley and Peter to carefully construct their alibis.

Riley is the 12-year-old middle child of the Greenburg family. She participates in the typical daily routines that her parents desperately try to maintain while exploring their open marriage.

Maisy is the 10-year-old youngest daughter of Ainsley and Peter. Her innocent questions about her parents' schedules force Ainsley and Peter to construct elaborate lies. She is easily comforted by their reassurances.