Ellen is a thirteen-year-old girl with autism who relies on her dot diary and careful planning to feel secure. She categorizes her life into manageable lists and uses stimming behaviors, such as rocking back and forth, to self-soothe. She speaks Hebrew with her parents and finds deep comfort in her family's Jewish traditions. During her class trip to Barcelona, she faces intense sensory input from crowded streets and constant changes to her schedule, testing her strict reliance on predictability.

Isa is a new student who joins the class just before the flight to Barcelona. They have purple hair and a half-shaved head, proudly identifying as nonbinary and pansexual while using they/them pronouns. Open and confident in their identity, Isa proves to be an observant teammate, actively helping Ellen find quiet spaces when the city environment becomes too loud.

Laurel is Ellen's longtime best friend, sharing a bond that stretches back to their early school years. Recently returning from a trip to Florida, Laurel increasingly focuses on fashion, makeup, and typical teenage interests. She spends more time with her newer friends during the class trip, creating friction as she struggles to accommodate Ellen's specific routines.

Abba is Ellen's father and a parent chaperone on the class trip. He works as a graphic novel illustrator and author, observing the students' dynamics while offering Ellen tools like noise-canceling headphones to manage the busy airport. He understands Ellen's emotional needs instinctively but gently encourages her to practice independence while away from home.

Andy is a friendly and calm classmate assigned to Ellen's scavenger hunt team. He is an enthusiastic fan of Abba's graphic novel series, enjoying the open-ended relationships between the characters. He harbors a secret crush on a local teenager named Xavi but hesitates to share his sexuality with the wider class.

Noah-James, who goes by Gibs, is a highly energetic member of Ellen's scavenger hunt team. He takes medication to help him concentrate and occasionally shows frustration when the group gets delayed. Despite his rushed nature, he brings enthusiasm to the team and quickly purchases a stuffed lizard named El Drac as a souvenir.

Señor L is the Spanish teacher and trip leader for the summer class excursion to Barcelona. He organizes a city-wide scavenger hunt to encourage the students to explore local architecture and culture. He frequently wears T-shirts featuring visual puns and oversees the daily itinerary.

Sophie-Anne is one of Laurel's other friends attending the Barcelona trip. She shares a conjoined bathroom with Laurel and Ellen at the Hotel El Búho. She enjoys activities like makeovers and shopping, reflecting the shifting social dynamics that separate Laurel from Ellen.

Madison is a classmate traveling on the Barcelona trip who rooms with Sophie-Anne. She frequently dictates her team's activities and shows a lack of understanding regarding Ellen's autism, eventually labeling Ellen's noise-canceling headphones as rude.

Meritxell is a Spanish teenager who visits Barcelona every summer with her brother. She catches Ellen's attention early in the trip, though she prefers spending her days shopping with Laurel's friend group rather than visiting local historical sites.

Xavi is a local teenager spending the summer at the same hotel as the students. He quickly becomes the subject of crushes for several students on the trip, including Andy, though he prefers leisurely activities over structured tourist excursions.

Ellen's mother remains at home in Georgia during the class trip. She provides a steady, comforting presence for Ellen from afar, participating in weekly Shabbat songs over video calls to help Ellen feel safe and connected to her routines.

Dr. Talia is Ellen's therapist back home. She provides Ellen with practical advice for managing anxiety, specifically teaching her to focus only on the things she can control when situations become unpredictable.

Laurel's mother handles the logistics for Laurel's travel arrangements. She answers the phone when Ellen calls in a panic, eventually coordinating the flight seat bookings with Abba.