Benjamin is a doctor, husband to Mimi, and father to Sarah and Theo. He lives in the suburban neighborhood of Avalon, where he watches his children grow up and slowly drift away. He possesses a quiet empathy and a lingering suspicion that time operates as a continuous loop rather than a straight line. He deeply loves his family but struggles to openly discuss their shared traumas.

Sarah is the eldest child of the Wilf family. As a high school student, she is a star athlete with excellent grades who projects confidence. In her adulthood, she works as a highly successful film producer in Los Angeles, juggling a demanding career and marriage. Outwardly, her life appears pristine, but she secretly relies on alcohol and risky behavior to suppress deep-seated guilt from her youth.

Theo is Benjamin and Mimi's son. As a teenager, he is highly anxious, deeply self-conscious about his weight, and feels vastly inferior to his popular sister. As an adult, he works late nights as a chef at a trendy New York City restaurant. He channels his pain into his culinary career, feeding others while keeping his own friends and family at a distinct emotional distance.

Mimi is Benjamin's wife and the emotional anchor of the Wilf family. She embodies unconditional maternal love, silently carrying her fears for her children's futures. In her later years, she develops Alzheimer's disease, which causes her to wander into the cold winter night in search of her adult children, whom she believes are still young.

Waldo is the highly intelligent, sensitive son of Alice and Shenkman. He relies on a stargazing app called Star Walk to find comfort in the vastness of the universe, a hobby that makes him a target for bullies at school. Feeling misunderstood and repeatedly punished by his father for his eccentricities, Waldo decides to run away from home, seeking refuge under the open sky.

Shenkman is Waldo's father and Alice's husband. Deeply dissatisfied with his life and terrified of repeating his own father's mistakes, he channels his frustration into aggressive, competitive sessions on his rowing app. He loves Waldo but finds his son entirely alien, frequently expressing his confusion through shouting and strict punishments that drive Waldo away.

Alice is Shenkman's wife and Waldo's mother. She works as a lawyer but finds her true focus at home, where she acts as a buffer between her husband's explosive temper and her sensitive son. She is fiercely protective of Waldo and grows increasingly furious with Shenkman's inability to accept their child for who he is.

Misty is a local teenager in Avalon and the object of Theo's intense crush. She joins the Wilf siblings on a spontaneous nighttime drive. Her presence in the vehicle sets off a chain of traumatic events that permanently alters the psychological landscape of the Wilf family.

Peter is Sarah's husband, a man living in Los Angeles who attempts to build a career as a screenwriter. His continued professional failures create tension within his marriage, forcing Sarah to financially support their upscale lifestyle while managing his bruised ego.

Lindgren is Shenkman's former college rowing teammate. He exists primarily as a digital avatar on Shenkman's exercise app, serving as a connection to a younger, more physically capable version of Shenkman's life.