Mallory is a single mother living in Connecticut whose life halts when her son experiences sudden kidney failure. She works as an artist and fiercely guards the truth about her son's parentage from her family. She wears a mysterious gold cobra bracelet inherited from her late mother, which connects her to a past she knows little about.

Hannah is a Hungarian refugee living in 1951 Egypt as the wife of an older British diplomat. Carrying immense grief from the family she lost during World War II, she initially seeks safety and emotional detachment in her passionless marriage. Her quiet existence changes when a life-threatening snakebite and a charismatic hotel manager force her to feel again.

Monk is a highly successful musician preparing to marry a popular internet influencer. Years earlier, he spent a formative summer on Winthrop Island where he pursued Mallory. He frequently clashes with his wealthy, controlling father, preferring his artistic ambitions over the corporate life his family demands.

Lucien is the Swiss-Alexandrian assistant manager at Shepheard's Hotel in 1951 Cairo. He acts quickly to save Hannah's life, sparking an intense connection between them. He possesses keen observation skills regarding the rising political tensions in Egypt and refuses to let Hannah hide her emotions.

Mr. Adams is Monk's wealthy, domineering father and a prominent patron of the arts on the East Coast. He uses his influence and money to maintain tight control over his family, expressing strong disapproval of Monk's musical ambitions while insisting his son attend law school.

Sam is Mallory's young son. After ingesting a death cap mushroom at camp, he suffers severe kidney failure and requires immediate, frequent dialysis while waiting for a donor match. He shares a striking physical resemblance to a famous musician.

Paige is Mallory's highly organized and practical sister. She frequently acts as the reliable emergency contact for the entire family. She encourages Mallory to seek out Sam's biological father for medical help and spends her free time investigating their late mother's adoption records.

Alistair is a British political liaison working in 1951 Cairo. He married Hannah after meeting her in a displaced persons camp. He displays arrogant and highly prejudiced attitudes toward the local Egyptian population, prioritizing his own comfort and status over the rising unrest in the city.

Lennox, who goes by Lee, is an Instagram-famous lifestyle influencer engaged to Monk in the present day. She projects a polished, camera-ready persona that contrasts heavily with Mallory's grounded lifestyle. She positions herself as highly empathetic but often behaves dismissively toward service workers.

Jànos is Hannah's first husband, a Hungarian philosophy student she married during the war. Her memories of their life together, and the severe tragedies they faced with their children, shape her emotional detachment in her current life.

Becca is Mr. Adams's third wife and the mother of his youngest children. During the 2008 timeline, she functions as Mallory's unpredictable and frequently difficult employer on Winthrop Island.

Chippy is Monk's younger half-brother. During the 2008 summer on Winthrop Island, Mallory works as his nanny, managing his high energy.

Blue is Monk's younger half-sister. Along with her twin brother Chippy, she spends the summer of 2008 under Mallory's care on the island.

Grace is the Portuguese housekeeper for the Adams family. She maintains a warm, familiar presence in the household and shows kindness to Mallory during her time as a nanny.

Jake is Paige's husband. He spends much of his time away from the family, leaving Paige to manage their household and navigate family emergencies alone.

Dillon is the boy Mallory briefly dates during college while trying to understand Monk's mixed signals. He reacts poorly to Mallory's lingering connection with Monk.

Lola is Paige's old friend from Yale. She owns a comfortable house on Winthrop Island and warmly hosts Paige and Mallory during their 2022 visit.

Sedge is Lola's brother-in-law, introduced to Mallory during her stay on Winthrop Island. He shows a clear romantic interest in her and offers an uncomplicated alternative to her past.

Lillian is the wife of another English diplomat stationed in Egypt. She socializes with Hannah and shares rumors regarding Lucien's history with other women in their diplomatic circle.

Barbara is Monk's aunt on his mother's side. She stepped in to raise him due to his mother's frequent absences, forming a close and supportive bond with her nephew that outshines his relationship with his parents.

Bernadette is the aging Mother Superior at St. Hilda's convent in Galway, Ireland. She vividly remembers the circumstances surrounding the birth of Paige and Mallory's mother decades earlier.

Luca is an appraiser friend of Mallory's who works for Sotheby's. He examines her inherited cobra bracelet to help determine its geographic origins and historical purpose.