Delsie is a seventh-grade girl living on Cape Cod with her grandmother. She is passionate about meteorology and often uses weather and ocean terminology to describe her emotions. Struggling with the absence of her mother and the shifting dynamics of her lifelong friendships, she feels increasingly isolated as the summer begins.

Ronan is a newcomer to Cape Cod, staying at the Seaside cottages where his father recently found work. He wears long black clothing despite the summer heat and quickly earns a reputation among tourists as an unruly presence. Underneath his guarded and defensive exterior, he demonstrates a quiet protectiveness toward local wildlife.

Grammy is Delsie's hardworking and loving grandmother. She cleans guest cottages to support herself and her granddaughter on Cape Cod. While she acts as a peacemaker in the neighborhood, she rigidly avoids discussing Delsie's mother, finding the subject too painful to confront.

Henry is a cheerful local fisherman who inherited his boat, the Reel of Fortune, from Delsie's grandfather. While his wife is temporarily away, he balances his fishing career with caring for his young daughter. He acts as a warm, paternal figure to the neighborhood children.

Esme is Henry's wife and a deeply empathetic neighbor to Delsie and Grammy. She freely expresses affection and frequently invites Delsie over to share her "nourishing tea." She provides the maternal warmth and open communication that Delsie craves during a difficult summer.

Tressa is a summer tourist on Cape Cod who quickly monopolizes Brandy's time. She is highly status-conscious and regularly mocks Delsie for being barefoot, wearing secondhand clothes, and living locally year-round.

Ruby is the young daughter of Henry and Esme. She misses her mother while Esme is temporarily away and frequently practices with a fishing line in her yard, which sometimes annoys the older neighbors.

Olive is the cantankerous next-door neighbor of Delsie and Grammy. She frequently complains about noise, objects to children playing in the yard, and is terrified of strong summer storms.

Brandy is a summer visitor who has been Delsie's friend since they were toddlers. This year, she arrives with new, more mature interests, showing a sudden disinterest in the rock-collecting and sandcastle-building they used to enjoy together on the beach.

Gusty is the newly hired maintenance man at the Seaside cottages. He is a former fisherman adapting to a new job and single parenthood, appearing gruff and highly protective of his private life.

Aimee is Delsie's theatrical and loyal year-round friend. Winning the role of an orphan in a play prompts her to ask Delsie insensitive questions about her background, unintentionally sparking Delsie's crisis over her absent parents.

Michael is a local friend of Delsie and Aimee. He spends his summers living in a local campground because his family rents out their permanent home to tourists. He struggles to relate to his cruel character in the play Annie.

Saucepan Lynn runs a local eatery and is known for her brusque demeanor. She has a unique management style, frequently instructing her regular customers to step in and cook their own food.

Mellie is Delsie's absent mother and Grammy's daughter. She left Cape Cod when Delsie was an infant. Delsie keeps her photograph and longs for her return, though Grammy firmly refuses to discuss her whereabouts or past.

Papa Joseph is Delsie's deceased grandfather. He was a skilled fisherman who mentored Henry and enjoyed using a metal detector on the beach, leaving behind a collection of small treasures that Grammy keeps.

Mrs. Fiester is Brandy's mother. She vacations in Cape Cod annually and treats her daughter to spa days, inadvertently highlighting the growing class and maturity differences between her family and Delsie's.

Madam Schofield is the exacting director of the local summer production of Annie. She pushes her young actors to look deeply into their own emotions to improve their performances on stage.