Elizabeth is a 30-year-old research chemist who unwillingly becomes the star of a nationally syndicated cooking show, Supper at Six. Operating in the late 1950s and early 1960s, she faces consistent discrimination from the male-dominated scientific community. She approaches cooking exactly as she approaches chemistry, using test tubes and precise measurements. She lives with her daughter and her highly intelligent dog, maintaining a strict atheistic and rational worldview.

Calvin is a brilliant, Nobel-nominated chemist working at the Hastings Research Institute. Raised in an Iowa boys' home after losing his adoptive parents, he holds a fierce grudge against the biological father he believes abandoned him. He prefers working in isolation and spends his free time pursuing his passion for rowing. He treats Elizabeth as an intellectual equal, distinguishing himself from the rest of the male staff at the institute.

Mad is Elizabeth's highly perceptive kindergarten-aged daughter. Due to a misunderstanding at the hospital during her birth, her legal name is simply "Mad." She reads at a sixth-grade level but pretends to be illiterate at school to avoid standing out. She pays close attention to adult emotions and feels intensely protective of her family.

Six-Thirty is a stray dog who adopts Elizabeth and Calvin. Originally a trainee for a military bomb-sniffing unit, he failed the program due to his fear of explosives. He possesses extraordinary intelligence, learning hundreds of English words, and silently communicates his protective thoughts regarding his human family.

Donatti is the insecure and sexist head of chemistry at Hastings. A former college rower who competed against Calvin, he masks his scientific mediocrity behind administrative authority. He actively resents Elizabeth for her intelligence and assigns her to low-level amino acid studies rather than the advanced research she spearheaded.

Lebensmal is the executive producer at KCTV and Walter Pine's direct superior. He views the female audience as intellectually inferior and demands that Elizabeth wear tight dresses and read simplistic cue cards. He routinely uses intimidation tactics to control his staff and enforce rigid gender expectations.

Harriet is Elizabeth's older neighbor who lives across the street. Trapped in an unhappy marriage to a heavy drinker, she watches Elizabeth's unconventional life through her windows before finally stepping in to offer childcare assistance. She provides Elizabeth with practical advice on balancing her personal identity with the exhausting demands of motherhood.

Walter is a television producer at KCTV and a stressed single father to Amanda. After Elizabeth confronts him about Amanda eating Mad's lunches, he offers Elizabeth a cooking show to fill a difficult afternoon time slot. He constantly worries about losing his job and struggles to manage the conflicting demands of his furious network boss and his decidedly unconventional new star.

Dr. Meyers is a prominent scientist at UCLA who supervises Elizabeth's master's degree. He uses his academic authority to sexually assault her. When she defends herself with a pencil, he leverages his institutional power to destroy her reputation and block her admission to the doctoral program.

Miss Frask works as a secretary in the personnel department at the Hastings Research Institute. She initially participates in the toxic workplace culture by spreading rumors about Elizabeth and treating her with hostility. She harbors her own secret pain regarding her past academic experiences, having been forced out of a psychology program.

Wakely is a reverend who leads a congregation in Commons, California. While studying at Harvard Divinity School, he struck up a written correspondence with Calvin Evans regarding the intersection of science and faith. He listens to the secrets of his parishioners while privately questioning his own religious beliefs.

Dr. Mason is an obstetrician who also captains the men's rowing team. He treats Elizabeth with straightforward medical pragmatism during her pregnancy. He recognizes her athletic capability and encourages her to continue rowing, dismissing the conventional mid-century medical advice that requires women to rest completely.

Dr. Boryweitz is an inept chemist working at the Hastings Research Institute. He frequently sneaks over to Elizabeth's workstation to ask her for help understanding his own assignments. He actively benefits from the institute's sexist hierarchy, allowing others to attribute Elizabeth's scientific breakthroughs to him.

Mrs. Mudford is the kindergarten teacher at Mad and Amanda's school. She strictly enforces behavioral norms and resents Mad for reading advanced books. She routinely gossips with other parents about the children in her class who come from single-parent households.

Amanda is Walter Pine's young daughter and a classmate of Mad. Because her father struggles to provide nutritious meals, she begins accepting the hearty lunches that Elizabeth prepares, which inadvertently leads to Elizabeth's television career.

Avery Parker is the wealthy philanthropist behind the Parker Foundation. She takes an active interest in the Hastings Research Institute and the scientists who work there. She corresponds through her legal representatives to direct funding toward specific scientific projects.

Wilson is a lawyer who handles affairs and endowments for Avery Parker. He acts as her intermediary, visiting the boys' home in Iowa and later investigating the funding situations at the Hastings Research Institute.

Franklin Roth is a reporter who attempts to write a serious piece about Elizabeth's scientific background. He finds himself clashing with his editors, who demand sensationalized gossip rather than a respectful profile of a female chemist.

Mr. Sloane is Harriet's husband. He is a bitter, heavy drinker who frequently acts abusively toward his wife, driving her to seek companionship with her neighbors across the street.