The book revolves around three main characters from three different eras: early Nazi Germany, 1980s Cuba, and modern-day Syria.
It follows Josef Landau, a German Jew in the 1930s, who tries to leave Germany to Cuba, Isabel Fernandez, a Cuban girl in 1994, who tries to escape Cuba's hunger crisis following the dissolution of the Soviet Union to the US, and Mahmoud Bishara, a Syrian youth in 2015 whose house gets destroyed by a missile and whose family decides to seek asylum in Germany.
Josef's story begins when his father Aaron gets taken away on Kristallnacht and is sent to the Dachau concentration camp by Nazi Stormtroopers.
While the passengers wait to be allowed to disembark, Josef encounters Mariano Padron (who is later revealed to be Isabel Fernadez's grandfather), who is a Cuban government officer bound by his governmental duty not to let the Jewish refugees in, despite feeling sorry for them.
Josef's maturation continues as the situation worsens: after his father attempts suicide, he alone is allowed to disembark for medical attention in Cuba.
However, when Germany invades and begins the occupying France at the end of the novel, the Nazis give his mother the choice of setting only one of her children free.
Josef sacrifices himself to relieve his mother from the burden of this choice, and to save his little sister Ruthie from the concentration camps.
Among the people who join Isabel on the journey is her grandfather Lito, who is eventually revealed to be Mariano Padron, the Cuban officer who, decades ago, prevented Josef from entering Havana.
Isabel spends much of the dangerous trip acting as an adult: she takes care of her eight-and-a-half-months pregnant mother, Teresa; she saves Señor Castillo when he is thrown overboard by waves; and she spends much of the trip relentlessly bailing out water from their boat so that they can continue their journey.