For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Tommo decides to flee his whaling ship when it lands at the French Polynesian islands, the Marquesas. He and his fellow sailor Toby make for the mountains, but they get more than they bargained for and end up more or less captive guests of the Typee tribe.
Act II
After Toby flees for help, Tommo learns to make the best of it in the Typee Valley. He learns the ways of the Typee as best he can, makes friends, and gets a little too comfortable.
Act III
After Tommo realizes that the Typee want to keep him there forever (and may or may not at some point kill and eat him), he decides it's time to go. When news of a boat at a nearby shore reaches the valley, our hero decides that it's time to skedaddle. After some negotiation and brawling, Tommo makes it to the British ship and freedom.