Josef is a 12-year-old Jewish boy living in Germany. Following his father's sudden arrest on Kristallnacht, Josef's childhood abruptly ends. He travels aboard the MS St. Louis toward Cuba, looking forward to his bar mitzvah while simultaneously shouldering immediate adult responsibilities. With his father mentally broken by the Dachau concentration camp, Josef attempts to act as the primary protector for his mother and younger sister.

Josef's father is a former lawyer who returns from the Dachau concentration camp deeply traumatized and paranoid. He constantly fears recapture and struggles to function. Josef's mother attempts to manage her husband's panic during their voyage to Cuba, negotiating with ship doctors for sedatives and relying heavily on Josef to manage the family's daily crises.

Isabel is an 11-year-old girl living in Cuba during the severe food shortages of 1994. She deeply loves her family and her trumpet. The instrument connects her to her cultural identity. When her father faces imminent arrest by local police, she trades her prized trumpet for gasoline to secure her family's passage on a makeshift boat bound for Miami.

Isabel's mother and father face immediate danger in 1994 Cuba. Her father is threatened with imprisonment by Castro's police, prompting their sudden flight. Her mother is pregnant, making the dangerous raft journey across the Straits of Florida physically perilous as the family seeks safety.

Abuelito Padron is Isabel’s grandfather and a former Cuban police officer. He joins his family on their makeshift raft to Miami but holds deep misgivings about leaving his homeland. He worries that Isabel will lose her connection to her Cuban heritage and carries unspoken guilt regarding his past actions in law enforcement.

Mahmoud is a 12-year-old boy living in the middle of the Syrian Civil War in 2015. He has learned that drawing attention to himself invites danger from local factions, so he adopts a strategy of total invisibility to survive. After a missile destroys his apartment building, he must endure an arduous trek across multiple countries. Throughout this journey, he constantly weighs whether staying hidden is truly the safest path for his family.

Mahmoud's parents make the sudden decision to flee Syria after their home is destroyed. His father maintains a persistent optimism and uses jokes to distract his family from their grim reality. His mother carries the heavy emotional burden of the journey, desperately trying to protect her children while facing impossible choices on the Mediterranean Sea.

Ruthie is Josef's four-year-old sister. She accompanies her family on their escape from Nazi Germany aboard the MS St. Louis. Due to her young age, she relies entirely on her older brother and parents for protection and does not fully comprehend the political dangers surrounding them.

Waleed is Mahmoud’s younger brother. He is a Syrian child heavily affected by the constant violence in Aleppo. He frequently displays a flat and emotionless reaction to the destruction around him, representing the psychological toll of growing up in a war zone.

Hana is Mahmoud’s infant sister. As a baby, she is entirely dependent on her family during their dangerous passage from Turkey to Greece. She represents the extreme vulnerability of the youngest refugees.

Iván is Isabel’s best friend and next-door neighbor. He works alongside his father to construct a boat from old metal advertisements and oil drums. He dreams of a better future in the United States and provides Isabel with companionship during their harrowing journey.

Señor Castillo is Iván’s father and Isabel’s neighbor. He designs and builds the makeshift metal boat that carries both the Castillo and Fernandez families away from Havana. He takes charge of the craft's rudimentary motor during their unpredictable crossing.

Luis is Iván’s older brother who has been drafted into the Cuban police force. He deserts his post, running through gunfire on the beach to jump aboard his father's boat at the last possible second alongside his girlfriend.

Amara is Luis Castillo's girlfriend and a Cuban police officer who deserts her position to flee the country. She proves resourceful during the sea crossing, offering practical suggestions to keep the overcrowded boat afloat in the stifling heat.

Captain Schröder is the German commander of the MS St. Louis. He is not Jewish but is deeply committed to finding asylum for his passengers. He defies the hostile members of his crew, treats the refugees with dignity, and actively negotiates with international governments when Cuba refuses them entry.

Captain Schiendick is a cruel, abusive Nazi crew member aboard the MS St. Louis. He actively torments the Jewish passengers, trashing cabins and threatening individuals. He represents the vicious antisemitism the refugees are attempting to escape.

Officer Padron is a young Cuban policeman stationed near the MS St. Louis when it anchors outside Havana. He actively participates in rescue efforts but also enforces the strict immigration policies that keep the Jewish refugees trapped aboard the ship.

Pozner is a Jewish passenger on the MS St. Louis who grows increasingly desperate as international governments turn the ship away. Unwilling to return to a German concentration camp, he attempts to organize a mutiny to force the captain to run the ship aground.

Mr. Nasseer is a former Palestinian refugee who has lived in Turkey for decades. He offers Mahmoud's exhausted family shelter in his shop and drives them to their smuggling boat. He pays forward the kindness he needed when he was displaced.

A taxi driver who picks up Mahmoud's family in Serbia. He initially presents himself as a helpful local offering a crucial ride, but he quickly exploits the vulnerable refugees for financial gain.

Ruth Rosenberg is an elderly German woman whose life is shaped by her experiences during World War II. She serves as a thematic link between the historical flights from Nazi Germany and the modern-day Syrian refugee crisis, understanding the desperation of displaced people.