The Mother is a writer undergoing a deep personal transition following her divorce. Struggling with creative block, she pulls her twelve-year-old daughter out of school to travel, ultimately landing in Catania, Sicily. She is deeply intellectual and introspective but battles intense anxiety over her own mother's potential dementia and her ability to protect her child during global and personal instability.

Ella is an inquisitive, resilient twelve-year-old on the cusp of adolescence. She is profoundly observant and possesses a rigid moral compass, insisting early on that their family's stolen Proteus mosaic must be returned. She engages deeply with classical mythology, actively seeking patterns in their daily lives to make sense of her chaotic environment.

Manuela Astroni is a distant but constant mentor figure living in Mexico. She communicates through cryptic, prophetic text and voice messages that often feature translations of classical texts. Experiencing the early symptoms of dementia, she remains intellectually engaged through her translation work and causes deep anxiety for her daughter.

The Tourist is a concert pianist whose apartment serves as a temporary refuge for the mother and daughter while he is on tour. He provides an extensive classical library that the family utilizes. His eventual return introduces tension and complicated dynamics into the mother and daughter's fragile new life.

Nanna is the family's foundational ancestor, a fiercely independent woman who once worked as a day laborer at an archaeological excavation in Sicily. She secretly stole a Roman mosaic depicting the sea god Proteus before emigrating to Mexico, leaving behind a complex legacy. She ultimately died in a psychiatric institution, establishing a family history of memory loss that haunts her descendants.

Vito is an elderly friend of the grandmother who resides in the coastal town of Poscello. He serves as a potential safe haven for the family as they travel across Sicily, offering a gentle, practical presence in contrast to the chaos around them.

The Telescope Man is an unnamed, eccentric companion of Vito living in the coastal town of Poscello. He spends his time studying the moon and offers a supportive, benign presence in the community.

Anna is a young art-history student working as a guide at the archaeological site of the Villa Romana del Casale. She provides historical context about the site's mosaics and the uncredited labor of local farmers.

The Absent Stepbrother is the son of the mother's ex-husband and a significant figure in the daughter's memory. His absence leaves a deep, unspoken grief, and his habit of taking Polaroid pictures heavily influences the daughter's desire to document her own life.