In the novel's first pages we're introduced to the book's initial conflicts, both big and small. First, the big picture: we're in the middle of a war. World War II, to be exact. Enemy German submarines have arrived in the Caribbean and are targeting the small island of Curaçao. The oil refineries and tankers in the area are valuable resources for the Allied war effort, so the German enemy forces want to take them out.
The situation on the international scene causes domestic strife in our protagonist's family, presenting us with another of the novel's initial conflicts. Phillip's mother wants to leave Curaçao and return to the family's home in Virginia; Phillip and his father want to stay put. In this way, we're presented with two tense situations: we see both a world at war and a family at odds with itself. The differences in culture between Curaçao and Virginia are set up in this section as well.
The novel starts hitting us with a whole lot of action. First, the ship on which Phillip and his mother are sailing is hit by a torpedo. Then, during the evacuation, Phillip is knocked out, and when he wakes up he's on a raft with a West Indian man and a cat. To make matters worse, Phillip's head starts hurting form his injury, and he goes completely blind. Adrenaline junkies should have their fix by now. This section also introduces us to the character Timothy, a West Indian man will play a big part in Phillip's character transformation. The tense dynamic between the two is set up here, as they embody the differences between American and Caribbean cultures.
The primary location of the novel shifts as Timothy lands the raft on a tiny cay in an area of the ocean known as the Devil's Mouth. Switching from war to survival mode, the desert island portion of the novel now begins in earnest. In the area of character development, Timothy and Phillip continue to clash as Phillip discovers that Timothy can't spell. Timothy pushes Phillip to help with chores even though he is blind. This irritates Phillip to no end, and he begins to regurgitate racist views he picked up from his mother.
The mounting tensions between Phillip and Timothy reach a climax as Timothy and Phillip finally have a major confrontation. Timothy goes so far as to hit Phillip, but after the fight, the two become friends. Phillip lets go of his racist views and realizes that Timothy is attempting to help him. Phillip's personal transformation is symbolically cemented when he triumphs over the palm tree, climbing it and grabbing its coconuts. Phillip also realizes that Timothy is old and sick. A role reversal begins to take place as Phillip starts helping Timothy. Along with all these personal revelations, the action of the novel reaches a climax as a massive hurricane hits the island. In this violent storm, Timothy gives his life to save Phillip, foregrounding the theme of sacrifice.
After the novel's climax we see Phillip develop his independence, alone now on the island except for Stew Cat. He rebuilds the shelter, cleans up after the storm, and is bitten by a moray eel. We also see his brainpower at work when he realizes that the signal fire isn't working because the smoke is white. He figures out how to make black smoke with the sea grapes. Growing stronger and more experienced every day, Phillip becomes a fully mature and independent young man.
In the novel's final pages all of the conflicts are tied up neatly. Phillip is rescued and reunited with his parents. The novel hints at their reconciliation, but Phillip struggles to tell them about his relationship with Timothy. The mother's character has changed, but there is no serious or satisfying dialogue between her and her son. In a deus ex machina move, a miraculous operation in New York restores Phillip's eyesight.
Phillip's maturity becomes most obvious in the novel's conclusion. He returns to his hometown to find out that his old friend Henrik seems very young now. Phillip hangs out with the West Indian people instead, because they remind him of Timothy. Later he will study charts of the Caribbean looking for the cay and longing to return.